The ISO has a "dos" partition table that presents it as having two partitions:
1) first partition of type 0 spanning blocks 0-759807
2) second parition of type ef (=EFI) spanning blocks 4040-5511

Just the "normal" multi-boot set up.

Use "fdisk -l $iso" to review that ..
perhaps VBOX fails to see the partition table? Or that its  virtual UEFI implementation fails to see it?

1) Why doesn't it boot? What does happen on the attempt?

Yes, the netinstall is supposed to work in UEFI mode, and there are many cases were it has done so.

One of the issues that may come up with the grub installation step is that for some reason the "efivars" have got filled up with some kind of dump files. This can be handled by the following slight manual hands-on just before selecting init system:

1. Shift to virtual terminal 2 by pressing Ctrl-Alt-F2, and push Enter.

2. Check if this might be the problem by command: ls /sys/firmware/efi/efivars/dump-*
   If that results with lots of output, then continue with step 3;
   if there is no such file, then this is not your problem, so skip step 3.

3. Remove the dump files with command: rm /sys/firmware/efi/efivars/dump-*

4. Return back to installer at virtual terminal 1 by pressing Ctrl-Alt-F1, and continue.

Did you already try with

ROOTFSTYPE=ext4

in /etc/initramfs-tools/initramfs.conf ?

Ok. My fault. I've let my team of developers drag their feet about getting forum translations installed and now there is a small pile waiting. I'm now reasonably hopeful though, that by having a big bowl of peanuts as bounty, they will succeed in making forum translation available for distributed maintenance in a near future.

@vgal, the filename attribute of the Packages file(s) contain the relative pathname to the packages, into the "pool" directory tree, which as you point out, has the subdirectories DEBIAN and DEVUAN, and below that, you find the further relative path into the publication servers' tree for the .deb file.

It does seem like apt-ftparchive does something else than reproduce the pool path from the associated Packages files, which I guess is in your step "# generate "Packages" file". Specifically, if you locate the associated Packages file snippet for the package concerned, either in the original-cd Packages file(s), or in your local /var/lib/apt/lists/*Packages, you will find the correct pool pathname for the package. Alternatively, you add a step to change the Packages files generated by apt-ftparchive by replacing all filename attributes with the correct pool/ relative pathnames as found in that pool.

@Jakoline I checked it out, and the rfkill package is actually in the ISO pool although not installed without DE. So the easier path would be to mount the ISO on, say, /mnt and then run

# dpkg -i $(find /mnt/pool -name \*rfkill\* )

(as root) to install it.

Thereafter you may follow the above good advice as to how to use it.

I think you should comment out that second eth0 configuration; if you need both ipv4 and ipv6 you'll need to combine them into a single configuration block, e.g. with "up" statements dealing with ipv6.

Do you have files in /etc/network/interfaces.d/ ? Where do the vlan adapters come from .. or what they are? Eg wan@eth0

EDIT: it looks like some kind of "openwrt" setup; could you post /etc/config/network if you have one?

You might want to try out the https://git.devuan.org/rrq/buster-to-devuan method although it's named badly for this purpose.

This is just a meta level note, that the way to capture bugs and user experience comments is by lodging "bugs", typically by email to the "bugs system".

The expectation is then that the lodger first tries to isolate which package is involved or seemingly involved and then lodge a "bug" against that package. If the package is "pure debian" the email target is "submit" at "bugs.debian.org, and if it's a devuan forked package, the email target is "submit" at "bugs.devuan.org,".

In both cases, the email should be a pure text email with the first two lines styled as

Package: packagename
Version: version

and then the description with details added.

It's of course fine to also note them at this forum, especially when it comes to more opinion based issues. However rather few of the package maintainers are at this forum.

mmm you omitted the -e... the last part of the line should read

-geometry 120x15-300+150 -e mail"

at least that's what the man xterm page says. I don't really know what the significant difference is between nominating a shell at the end (without -e) and nominating a program via the -e option. The man page has some discussion about it, but the authors' idea of clarity is different from mine.

To use double-quotes within a double-quoted string, they must be back-slashed... ie

coolmail -e "xterm -xrm 'XTerm.vt100.allowTitleOps: false' -T \"System mail notification\"" -geometry 120x15-300+150

An alternative is to use single-quotes, as in the -xrm detail.