The embedded install.rdf should state what versions the plugin is compatible with. Mine (a.o. storage scanner, but not DOI manager) declare compatibility with 5.0.*, although I practice I only provide support for the latest public release of Zotero.
Ah, that. I don't anticipate storage scanner to be affected, but it doesn't run nightly tests like BBT does. The main relevant change was that default prefs are no longer loaded right? Storage scanner doesn't have any preferences.
It looks like @bwiernik updated DOI Manager in October, so that should be compatible.
Storage Scanner hasn't been updated since 2018, but I'm guessing it wasn't affected by the 5.0.78 changes?