How is the database migration support for these tools?

Needing to support clients that don’t phone home for an extended period and therefore need to be rolled forward from a really old schema state seems like a major hassle, but maybe I’m missing something. Trying to troubleshoot one-off front end bugs for a single product user can be real a pain, I’d hate to see what it’s like when you have to factor in the state of their schema as well

I can't speak to the other tools, but we built PowerSync using a schemaless protocol under the hood, specifically for this reason. Most of the time you don't need to implement migrations at all. For example adding a new column just works, as the data is already there when the schema is rolled forward.