haven

TruffleRuby supports many C extensions like DB adapters out of the box like CRuby. JRuby has Java ports for most popular gems that ship alongside them. Nokogiri is one gem that's a Rails dependency and stands out as a bit of a pain, but both JRuby and TruffleRuby put in substantial effort to support it too. All three generally work with web servers, including Puma, which ships with Rails. There are still gaps in C extensions that TruffleRuby covers and lack of Java ports for less popular but still used gems. They may have some things like gRPC C extensions that don't work and they don't want to port them either. Generally the ecosystem just works between these popular Ruby implementations.

MRuby uses MGems and is just a different ecosystem entirely. It has parallel libraries but they're not shared with the above implementations.

Signature. The Ruby::RBS library used to be called Ruby::Signature.

Not to nitpick, but a quick check shows Square has way more stars overall. (233,343 stars for Square repos and 30,982 stars for Stripe repos.) If you’re talking about Square’s brand new SDKs, they of course start with zero stars and some are just weeks old.