This is partly covered in the GitHub Readme of TruffleRuby: TruffleRuby can run Rails and is compatible with many gems, including C extensions. However, Tr

This is partly covered in the GitHub Readme of TruffleRuby: TruffleRuby can run Rails and is compatible with many gems, including C extensions. However, TruffleRuby is not 100% compatible with MRI 3.0 yet. Please report any compatibility issues you might find. TruffleRuby passes around 97% of ruby/spec, more than any other alternative Ruby implementation. TruffleRuby might not be fast yet on Rails applications and large programs. Notably, large programs currently take a long time to warmup on TruffleRuby and this is something the TruffleRuby team is currently working on. Large programs often involve more performance-critical code so there is a higher chance of hitting an area of TruffleRuby which has not been optimized yet. However, I think this is slightly outdated, because I vaguely remember a talk from one of the rubycons about Rails being slightly faster with truffle. I can't say for sure why it's not been widely picked up yet; maybe other players are looking forward to JITs within Ruby itself, or don't like the two tier model of GraalVM (you can run it for free, but it also has an enterprise version with additional performance improvements.)