Ubuntu is a fork of unstable Debian packages

And where do you think debian stable packages come from exactly ?..

it’s basicaly the exact same thing. In both case :

• At some point freeze unstable (snapshot unstable in case of ubuntu),
• fix bugs found in the frozen set of packages,
• release as stable.

Not if root account is disabled. Which is by default on Ubuntu and Debian . You’d need sudo su - but well… No sudo left you know.

I tried to convert Debian to Ubuntu by replacing the Debian repos in apt with Ubuntu’s and following with dist-upgrade

Shouldn’t it work though ? Or be close to work with the appropriate options passed down to dpkg

It doesn’t work with root disabled.

The way to fix this is to boot in bash recovery where you land a root shell. From there you can hopefully apt install sudo if deb file is still in cache. If not, you have to make network function without systemd for apt install to work. Or, you can get sudo deb file and all missing dependencies from usb stick and apt install them from fs. Or just enable root, give it a password and reboot so you can su - and apt install sudo

• apt something that ended up removing sudo. No more admin rights.
• used rsync to backup pretty much everything in / , with remove source option…
• find with -delete option miss positioned. It deleted stuff before finding matching pattern
• chown / chmod on /bin and/or /usr/bin
• Removed everything in /etc