Not much use to go Ubuntu or Mint, unless you have specific issues with Debian that don’t happen with those. Even then, it may be one apt install
away from a fix.
If you want to try out BSD, power to you. I wouldn’t experiment on a backup computer though, unless by backup you just mean you want to have the spare hardware and will format it with Debian if you ever need to make it your main computer anyway.
Otherwise, just run Debian!
The main “instability” I’ve found with
testing
orsid
is just that because new packages are added quickly, sometimes you’ll have dependency clashes.Pretty much every time the package manager will take care of keeping things sane and not upgrading a package that will cause any incompatibility.
The main issue is if at some point you decide to install something that has conflicting dependencies with something you already have installed. Those are usually solvable with a little
aptitude
-fu as long as there are versions available to sort things out neatly.A better first step to newer packages is probably
stable
withbackports
though.https://backports.debian.org/