So... short answer; start from scratch. I've got a handful of weewx instances for various purposes, all on 4.10.2 or whatever the
last 4.* release is. I haven't tried weewx 5.x (I did but left it alone), but my actual gripe is with python's overlords disallowing
PIP installs into the main system. I can sort-of "get" the point of the attempt to not pollute a Linux distribution, but I resent
Python's intrusion into my decisions about what's best for me.
Probably not a popular opinion, and completely unrelated to weewx, but here we are. FWIW, I'm also behind on version of PiOS
releases specifically because of this python/pip stuff.
To your question; how did you install in the first place? Packages can be uninstalled and specific versions re-installed.
Chris