Is there any documentation available for having a TemplateVM on based Debian with Tor connection only? I mean: I would love to create a new TemplateVM on based Debian only and with this new TemplateVM I would install Tor Browser, Cwtch and whatever connects with the Tor / Onion. I think it is a good way to have a separated TemplateVM which connects to Tor. Between: I have seen that there are many Apps which connects to the Tor:
Alternative will be with Whonix on Qubes OS. I know and I also tried it. But Whonix is “disposable”. Once any apps are installed there, after restarting the Whonix, all installed app will be removed. Also fair regarding the concept / methodology.
You can create whonix AppVMs, templates, and standalones, not only displosables.
It depends on whether you want to enforce tor connectivity or not. If you want to enforce it, see isolating proxy (spoiler: whonix is the easiest way to do this in qubes, use whonix or set whonix proxy as the net qube). If your goal is for the apps to be able to connect to the internet directly as well as over tor, just set up a conventional template with tor-capable applications by following generic documentation and / or community guides on flatpak, snap, etc.