Dev setup missing (a check for) ocrmypdf?

[bikubi]

Document uploader images-to-PDF conversion failed silently (for me), no warnings.
The POST request is successful, and returns an id with file path to a PDF, but the object+file does not exist, it is immediately removed.

Cause: convert_images_to_pdf_task https://github.com/okfde/froide/blob/main/froide/foirequest/tasks.py#L254 fails because the shell_call to ocrmypdf fails in https://github.com/okfde/django-filingcabinet/blob/main/src/filingcabinet/pdf_utils.py#L388.

I can see a reference to ocrmypdf in dev.nix; locally I had to install it via package manager, plus tesseract language pack(s).