P.S.
I searched and there’s another thread from a few months ago that hints at the problem being install-time setup. Here is the thread (and yea it’s a bit long, and has no conclusive fix):
Tesseract on Nextcloud AIO docker - 
Features & apps / ocr - Nextcloud community
Based on your post and the other thread, I’m guessing that the AIO or docker installs do not setup the combination of services needed (so Tesseract + Elasticsearch, and their ports, any TLS certs, their file permissions; plus the language packs, etc.) and a manual install is needed to verify that each component is working.