Thank you for the donation.

My idea: Debian Bookworm real 32bit system without GUI and then install Retropie?

Not quite - use Debian with a minimal GUI (XFCE/LXDE) and a 64 bit system. On a PC, RetroPie is meant to be used from a desktop session (X11/Wayland). Next week the new Debian Trixie (stable) version will be released and there will be no more 32bit installation images (just like Ubuntu/Fedora/other distros), so use the 64 bit installation image.

I don't think you'll be able to use Ubuntu 16 to install RetroPie, even if you check out the 4.5.1 version - most of the packages will not work with that old Ubuntu version.
You can try installing the current Debian release or a more recent (18.04) Ubuntu version and install RetroPie as explained in the docs.

@barbudreadmon Looking at the Udoo website, this is a much more powerful device than mine with better processor, graphics and more RAM. I think this explains why I can't emulate PSOne on such an old low-end machine.