Which, as far as I found so far, means Forgejo. Haven't found any others. And even Forgejo Actions says that it's mostly the same as Github Actions syntax, mean

Which, as far as I found so far, means Forgejo. Haven't found any others. And even Forgejo Actions says that it's mostly the same as Github Actions syntax, meaning you still have to double-check that everything still works the same. It probably will, but if you don't know what the corner cases are then you have to double-check everything. Still, it's probably the best migration option if you rely on GHA.