IMO Linux is gradually becoming a poor fit for niche use cases and extremely constrained devices. It makes sense, as they are trying to trim less used parts of the code that add maintenance overhead (especially areas without any volunteers to maintain them). And RTOSes are gradually replacing Linux on MCUs. I don’t know what’s best to replace it if you want a full OS, probably NetBSD?

Edit: I looked into it, sounds like NetBSD hasn’t done work on ESP32 before because of the lack of MMU. Now this should be possible, but there’s probably a fair amount of work to do.