I'm still collecting info, but locally this seems to work with 12.5.1 but not 12.4 (I have both installed here). We're using Github actions for CI, which (currently) only supports 12.4. There's a private preview of 12.5 and we're attempting to get into it, but I think we're going to run into other CI issues as we're publishing an SDK that other groups use. We were using Carthage previously, which was a nightmare, and the move to SPM seemed really easy, but this is a huge blocker now. Hoping to find a workaround, but reading above, that seems unlikely :)