I've followed this Salesforce blog Drive your Testing Strategy with Code Coverage to get LWC and Apex code coverage numbers reported in Codecov via GitHub actions. The LWC part works well, but it appears that the Apex test results cause Codecov to get stuck "Processing...".
Have you experience and solved this problem for Apex?
(Yes I have a ticket raised with Codecov as well and will post any solution they provide here. But this appears to be Salesforce language specific i.e. Apex problem that someone on this site may have experienced.)