Apologies for late reply. I have exactly the same issue as in File import callback not supported
This is not a new issue IMHO and just a caveat that this also happens in Mac. I tried to use the
contract Counter is GSNRecipient {
but the import import “@openzeppelin/contracts-ethereum-package/contracts/GSN/GSNRecipient.sol”;
never resolves. My gut says that truffle is not playing well with openzeppelin. I haven’t got a chance to dive deeper into this.