Coveralls is not working properly for us (at least I keep getting 500 every time I try to access a file there). The main reason we moved to Coveralls was poor support for PRs from forks on the CodeCov action. CodeCov made some changes recently which should fix that (https://github.com/codecov/codecov-action/issues/29), so it's probably safe to move back to CodeCov.
Coveralls is not working properly for us (at least I keep getting 500 every time I try to access a file there). The main reason we moved to Coveralls was poor support for PRs from forks on the CodeCov action. CodeCov made some changes recently which should fix that (https://github.com/codecov/codecov-action/issues/29), so it's probably safe to move back to CodeCov.