Hey, Tim! Thanks for looking.
Why 4.2.0? Looking back, it is what the TinaCMS self-hosted starter's Dockerfile used, and we didn't think to question it until we were deep in ESM hell. We ended up having to install Node 22 via n and nuke the base image's Node 18, which is exactly the kind of thing a newer base image would have avoided. If 5.0.0 ships with Node 20+ that alone would eliminate Showstopper #5 (the ESM compatibility hydra that ate most of our time).
The repo: Here it is: https://github.com/OrcVole/tinacms-cloudron
Fair warning: it's in a "works up to the last mile" state. The Docker image builds, health checks pass, admin UI loads, auth works, and the GraphQL API returns JSON. But schema indexing into MongoDB never completes, so the editor can't actually load content. If someone familiar with TinaCMS internals (or Cloudron base 5.0.0) wants to take a crack at that final piece, the groundwork is all there.
Would switching to base 5.0.0 and its native Node fix the indexing step too? That's the bit we never got past. The tinacms build --skip-cloud-checks command (without --skip-indexing) just prints "The service was stopped / Unable to build" with no useful error output.