I used devuan Daedalus (now Excalibur) with LXDE and Networkmanager and it works.
Try this:
If you are using Netinstall anyway, deselect everything.
After rebooting, install LXDE and Networkmanager as follows:

sudo apt install lxde-core network-manager-gnome

oder

sudo apt install --no-install-recommends lxde-core
sudo apt install network-manager-gnome

The second is my way, because I don't know what is in the meta package lxde-core for recommendations

For me (lxqt), the sudo pm-suspend works, but only after a new boot.
If you (in one session) first try to go in suspend with the mate utils, then pm-suspend has the same behavior. Thats important.

I have added in sudoers file

mikey ALL=NOPASSWD: /sbin/pm-suspend, /sbin/pm-hibernate

So you can make a button (desktop, panel) with "sudo pm-suspend"

I think this is a bug and has to report.

As I wrote in my first post:
The attempt to install a more recent version from Debian fails due to missing dependencies.

Yes indeed, the version of Falkon in Daedalus is the same as in Debian Stable/Bookworm.
I also don't think Falkon depends on systemd.

But Daedalus came out a year ago.
It cannot be that an internet browser that can be installed via the normal repos is already outdated.
What should be in one or two years?
It's not just the messages, e.g. t-online email can no longer be used properly.

P.S.: I cannot find this list of forbidden packages.