Pants was inspired by Blaze! @enough-analyst-54434 and @happy-kitchen-89482 were Xooglers, and missed that tooling once they moved on to other companies. Pants 2 is a significant departure from those long-ago roots, but no doubt you will notice the influences still.
We currently support a number of languages including of course Python and Java. TypeScript is on the agenda for the near future, but no timeline yet. We haven't got R support on the roadmap yet, but would welcome someone interested in contributing and are always glad to help. @wide-midnight-78598 has been working on a C/C++ experimental backend, so it's legit viable to pursue that kind of thing.
(As an aside, my company Toolchain is the lead sponsor of Pants and we are available for Pants feature contracting when an org would rather pay someone else to take care of contributing a feature their team needs.)