Comment by onion2k

I've dreamed about a 20% policy like google had, except it's where you can work on anything, including code debt.

Where I work we have 1 'maintenance day' each sprint where the devs choose what to work on. That can be fixing annoying issues, improving the code, learning something, trying something out, etc. It works well when other things aren't taking priority (which is far too often tbh).