Isabelle also has a fairly large set of mathematical proofs and supporting libraries, see https://www.isa-afp.org https://www.isa-afp.org. People routinely pub

Isabelle also has a fairly large set of mathematical proofs and supporting libraries, see https://www.isa-afp.org https://www.isa-afp.org. People routinely publish new proofs there, it is actually a regular referred journal.