Thanks for sharing the all this!
Possibly similar/related:
- Mimetype Warning after upgrading to 28.0.9 or 29.0.5 - #18 by tomspatz
- Some files have not passed the integrity check: "Invalid files" during integrity scan
- Integrity check error for core/js/mimetypelist.js since update to 22.2.5
- [Bug]: Warning: One or more mimetype migrations are available · Issue #47359 · nextcloud/server · GitHub