I am blaming NO one!!
I just want people to avoid the trap of such a case!
I'm no politician and no flamer, so please stay on the subject.
Anyway, you gave me the good hint earlier, thanks for that.

The new version of networkmanager (debian)

As previously mentioned, network-manager is already a forked packge proivided by Devuan.

Cause: Failure to read the NEWS file or sufficiently test the default desktop install.
FTFY.

Why are you tring so hard to assign blame? This is not a Debian bug, nor is it Debian's fault. Rather it was an intentional, documented change (2 years ago at at that), which Devuan failed to react to.

Bug found, bug fixed. Case closed. If you really feel the urge to couch it in terms of the "us vs. them" nonsense so popular around here, at least try to get the facts straight.

I have no idea where such a suggestion is to be posted. I think Devuan's administrators could come to the rescue.
Thank you.
Andre

There is news about our config NetworkManager-OpenRC-Cinnamon: the differences between Devuan Excalibur and Artix.
See the differences in the following reports I have just written:
Excalibur:
https://pastebin.com/4CcBTkEV

Artix:
https://pastebin.com/3KuU9mUy

In the Artix test-install (~6 month old), there is a additional file in /etc/NetworkManager/dispatcher.d/
-rwxr-xr-x 1 root root 1213 May 14  2021 10-openrc-status

And the version of networkmanager is networkmanager 1.54.1-1
The result is that NFS mounts in /etc/fstab are respected at boot time.
I have the additional file here should you be interested.

I will send the same information to the devuan networkmanager maintainer.
Have a lovely Sunday. Greetings, André.

Bugreport
https://bugs.devuan.org/cgi/bugreport.cgi?bug=925

So then until an Excalibur patch comes out with future updates, we will have to do as steve_v suggested. I'm happy with that.
I think that what was asked for.
Greetings,
andre4freedom

I have just done that. Thank you.
Bugreport sent.

Shall I mark the case as solved?

Thank you for your suggestions and help, to all!

You could file a bug report against network-manager requesting that the missing file be restored. We already fork that package, so the report goes to bugs.devuan.org. I find email submission to be the easiest.

Instructions:
https://bugs.devuan.org/Reporting.html

@ralph.ronnquist
I did the tests on a spare machine, doing a fresh-install with the excalibur-netinstall-iso and running the the devuan installer's first option: install
Test 1:  Excalibur - Cinnamon - OpenRC
Test 2:  Excalibur - Cinnamon - sysvinit
In both cases I just edited the hosts file, the fstab, created the mountpoints and rebooted. In both cases NFS was not mounted.

Copying the famous file /etc/NetworkManager/dispatcher.d/01-ifupdown from my local server (daedalus)  to the test machine did the trick..
BTW: Editing the /etc/rc.local file didn't change a thing.

Would you like me to write a simple procedure (a text file) how to fix that problem? Then, where could I send it for inclusion to the release readme file?

Unfortunately I'm not able to fix the networkmanager package.

Once again, to all of you: Thank you for your help.
Sincerely, Andre (andre4freedom)

https://dev1galaxy.org/viewtopic.php?pid=57261#p57261

which referenced /lib/init/init-d-script and so i went and saw that a bit of it referenced "mountnfs.sh" with some content/context referencing the words "after" and "before" and so i post the snippet of code here below:

# PATH should only include /usr/* if it runs after the mountnfs.sh
# script.  Scripts running before mountnfs.sh should remove the /usr/*
# entries.
PATH=/usr/sbin:/usr/bin:/sbin:/bin

also at the end of /lib/init/init-d-script there was a reference to:

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=822753#53

and that link drops one into the midst of just one of many "discussions" which seem not so distant from some of those on this forum...(*cough* hat-tip @steve_v)

as always, ymmv.

edited to add: also wanted to quote a snippet from message#36 in the same above noted "discussion"

Dmitry Bogatov may *not* volonteer(sic) to _fix_ them...nevertheless, there be dragons...sigh.

So obviously, would I want to use nfs, I need to arrange for that by myself since I wouldn't find joy in associating nfs mounting with networking events.

And if I choose to install a system with a Devuan installer iso and select a desktop flavour that installs NetworkManager, I will need some additional post-install hands-on to purge that together with apparmor, avahi-daemon and whatnot that the desktop flavour developers have included at the outside of my ideal setup.

it seems the default setup case is the invocation at line 90

I read it the other way:

        # Using 'no !=' instead of 'yes =' to make sure async nfs
        # mounting is the default even without a value in
        # /etc/default/rcS

/etc/default/rcS as shipped with initscripts has '#ASYNCMOUNTNFS=yes', so

87          if [ no != "$ASYNCMOUNTNFS" ] ; then

is true, and the do_wait_async_mount loop runs until timeout or all mounts appear.

i.e. async mount (AKA just loop while waiting for the network initscript / manager / whatever to call the mountnfs hook) is default behaviour as per the comment, and /etc/init.d/mountnfs.sh only calls /etc/network/if-up.d/mountnfs itself if the user has explicitly disabled async mount.

...which neatly explains the conspicuous lack of attempts to mount NFS in Andre's logs on a fresh install with networkmanager, and the "works same as it always did" for those using ifup and static definitions in /etc/network/interfaces (me, and I suspect you as well).

Seems to me that if Devuan is going to use networkmanager in the default desktop install (connman is going away and all that) and we want fstab NFS mounts to work, the obvious solution would be for Devuan to fork the networkmanager package and put /etc/NetworkManager/dispatcher.d/01-ifupdown back where it belongs.

NFS mounts are set up as declared in fstab via the init script mountnfs.sh, and it's not as a side effect of networking.

Here is initscripts: /etc/init.d/mountnfs.sh

#! /bin/sh
### BEGIN INIT INFO
# Provides:          mountnfs
# Required-Start:    $local_fs
# Required-Stop:
# Should-Start:      $network $portmap nfs-common  udev-mtab
# Default-Start:     S
# Default-Stop:
# Short-Description: Wait for network file systems to be mounted
# Description:       Network file systems are mounted by
#                    /etc/network/if-up.d/mountnfs in the background
#                    when interfaces are brought up; this script waits
#                    for them to be mounted before carrying on.
### END INIT INFO

. /lib/init/vars.sh
. /lib/init/mount-functions.sh
. /lib/lsb/init-functions

do_wait_async_mount() {
	# Read through fstab line by line. If it is NFS, set the flag
	# for mounting NFS file systems. If any NFS partition is found
	# then wait around for it.

	waitnfs=
	for file in $(fstab_files); do
		if [ -f "$file" ]; then
			while read DEV MTPT FSTYPE OPTS REST; do
				case "$DEV" in
				  ""|\#*)
					continue
					;;
				esac
				case "$OPTS" in
				  noauto|*,noauto|noauto,*|*,noauto,*)
					continue
					;;
				esac
				case "$FSTYPE" in
				  nfs|nfs4|smbfs|cifs|coda|ncp|ncpfs|ceph)
					;;
				  *)
					continue
					;;
				esac
				case "$MTPT" in
				  /usr/local|/usr/local/*)
					;;
				  /usr|/usr/*)
					waitnfs="$waitnfs $MTPT"
					;;
				  /var|/var/*)
					waitnfs="$waitnfs $MTPT"
					;;
				esac
			done < "$file"
		fi
	done

	# Wait for each path, the timeout is for all of them as that's
	# really the maximum time we have to wait anyway
	TIMEOUT=900
	for mountpt in $waitnfs; do
		log_action_begin_msg "Waiting for $mountpt"

		while ! mountpoint -q $mountpt; do
			sleep 0.1

			TIMEOUT=$(( $TIMEOUT - 1 ))
			if [ $TIMEOUT -le 0 ]; then
				log_action_end_msg 1
				break
			fi
		done

		if [ $TIMEOUT -gt 0 ]; then
			log_action_end_msg 0
		fi
	done
}

case "$1" in
    start)
        # Using 'no !=' instead of 'yes =' to make sure async nfs
        # mounting is the default even without a value in
        # /etc/default/rcS
        if [ no != "$ASYNCMOUNTNFS" ] ; then
                do_wait_async_mount
        else
                FROMINITD=yes /etc/network/if-up.d/mountnfs
        fi
        ;;
    restart|reload|force-reload)
        echo "Error: argument '$1' not supported" >&2
        exit 3
        ;;
    stop|status)
        # No-op
        ;;
    *)
        echo "Usage: $0 start|stop" >&2
        exit 3
        ;;
esac

:

Feel free to point out where it mounts NFS filsystems "not as a side effect of networking", because I sure don't see any calls to /bin/mount, and the header quite clearly contradicts your statement:

# Description:       Network file systems are mounted by
#                    /etc/network/if-up.d/mountnfs in the background
#                    when interfaces are brought up

That sure sounds like a "side effect of networking" to me (and it needs to be, since starting networkmanager doesn't indicate whether or not it successfully brought up an interface via exit codes, rather it backgrounds immediately expecting systemd to query status over dbus).

All that init script does is loop until the filesystems exist in /proc/self/mountinfo, so that other scripts can use it as a dependency. Actually mounting NFS filesystems is handled by:
a) systemd network.target, if /run/systemd/system exists.
b) /etc/network/if-up.d/mountnfs, as called by ifup.
c) /etc/network/if-up.d/mountnfs, as called by networkmanager-dispatcher.

a) is obviously not going to happen
b) is not how the OPs system is configured, they're not using ifup / /etc/network/interfaces.
c) is broken in Excalibur, because Debian networkmanager behaviour has changed (since Debian uses option a now) and no replacement has been shipped.

Well unless Andre4freedom is just making things up, it clearly does not when the network is managed by networkmanager.
If you don't want to actually look at the logs you asked for, read the shell scripts you reference, or offer any constructive advice... You do you.

@Andre4freedom: You might try grabbing that missing file (/etc/NetworkManager/dispatcher.d/01-ifupdown) from the Daedalus network-manager package. Like I said I don't have a system to test it on, but the manual suggests networkmanager should still call it if it exists.
Add some printfs (or drop a 'set -x' for mondo verboseo) in the relevant scripts if you need more info on what is going on... There are no NFS related errors in your logs, and I'm pretty confident that's because nothing is even trying to mount NFS right now.

Clearly one may insist on some different NFS mount behaviour.. In such a case one will need to set up the system to support that.