When you go marketplace, and search for a plugin name not exist, it will return an error screen. See screen capture.
@peterhashair I'm not able to reproduce that locally. Are you maybe able to give some more details on the request that is failing?
But while testing I found another regression, which will be fixed with https://github.com/matomo-org/matomo/pull/19529.
@sgiehl close the ticket, sorry I was on development enabled=1.