Finally!
Batch export of object metadata and an #oai interface have come to #museumdigital
https://blog.museum-digital.org/2025/11/24/making-interoperability-easy/
Considering I first looked into implementing OAI-PMH at museum-digital in what must have been 2015 or 2016, this really has been a long time coming.
The praise the Städel Museum deserves for their positive example cannot be overstated. The idea to use JSON in the resumption token is wonderfully simple, but reduces the pain of implementing and hosting OAI-PMH so much.