I ran into it while looking for info. If I understood correctly, the new planet is at: https://github.com/openSUSE/planet-o-o which seems to involve ruby and jekyll.
We use planet pluto, which is a ruby implementation, which generates posts in a way that's parsable by jekyll, which we use everywhere in our infrastructure to generate static pages.
The same script was adopted by KDE: https://invent.kde.org/websites/planet-kde-org/
I am also preparing a version for Bugzilla: https://github.com/hellcp/planet-bz-o Which you can preview on https://planet-bugzilla.lcp.world/
You could just skip the jekyll stuff, if it doesn't integrate well into your setup, but we base pretty much everything on jekyll, so it was a great way to integrate planet into the rest of our infrastructure
Oh yeah, and pluto upstream is great, both we and KDE guys sent PRs their way and they were quick to respond and merge them. If you aren't afraid to use ruby, it's very nice
The old planet was at: https://github.com/openSUSE/planet.opensuse.org and apparently was also relying on old code (py 2.6 looking at the libs folder in there).
That's rawdog, I gave up on making it py3 fairly quickly ;)
LCP [Stasiek] https://lcp.world/