Preface: I'd already upgraded an Unstable installation that I used for... testing, anyway, to the 20.04 base - with no issues whatsoever.
I was kind of wary of doing so with my daily working rig - User edition.
Mainly because I have a few old(ish) apps - that mostly depend on Python2 - that I could not get to work on Kubuntu 20.04

What I did: I cloned my current working rig to another partition (changed the UUID, fixed fstab ;·) and set it not to use my (separate) /home as /home.
Used the same hostname/username. Copied the relevant stuff from my /home to its /home.
Did the dist-upgrade on that. It took a while, but it worked. No issues.

What I got: A working neon User, Ubuntu 20.04 based, where all my Python2-based stuff actually worked.
Identical in all respects to the daily work one. Nice. Tomorrow (it's 9:30 PM here) I'll set it to use the same old /home, do some more testing, but it's looking good.