I am not a big fan of snap, and I would prefer a more logical and unified package management system

That’s exactly where Snap is going!

Seriously tho, Ubuntu is fine. The LTS versions are always extremely solid. Your objections sound more theoretical than practical and you also seem to be running quite advanced hardware and software. The least risky strategy would be stay where you are.

The options are surprisingly poor.

Personally, I rolled my own TUI script. It uses pdftk to explode and merge, and gs (Ghostscript) to optimize. To paste PNGs of my signature (absurd, but here we are) I use xournal, which looks a bit rough but gets the job done.

Exactly. OP should start by seeing what’s possible in Firefox.