Ubuntu Studio 24.04, OBS 32.0.0: Plugin Errors

[AaronD]

Log and Analyser:
https://obsproject.com/logs/zQB5MPorc7wx4EEG
https://obsproject.com/tools/analyzer?log_url=https://obsproject.com/logs/zQB5MPorc7wx4EEG

I added the official PPA a long time ago:
https://obsproject.com/forum/threads/ubuntu-ppa-installation-instructions.16495/
sudo apt-add-repository ppa:obsproject/obs-studio
The normal system updates then grab the latest supposedly-stable version of OBS, and that worked for a long time. But when it got version 32, it did this:

So I closed OBS, got the latest installers for those and ran them, and restarted OBS.
https://obsproject.com/forum/resources/source-defaults.1628/
https://github.com/CodeYan01/source-defaults/releases/tag/v1.1.1
https://obsproject.com/forum/resources/downstream-keyer.1254/
No change. Still gives that error on startup. The Source Defaults went away, but the Downstream Keyer seems to work anyway. So I don't think it's *only* a plugin problem. If it works, don't say it "failed to load." There might be a different problem, but that's not it.

Anyone know what the problem *actually* is, behind that message?