Cannot deal with dotless upstream versions, or epoch

Trying to package libargon2 (whose version is 20190702) for our infrastructure, I can't seem to come up with a version scheme that I could go with, RE_NVR's set up requires a dot in the version (so 20190702 alone won't fly) yet there's no way to include an epoch (1:0~20190702, which aren't traditionally encoded in the archive name). Is pretending the version is 20190702.0 really meant to be the only option in my case or can split_archive_fn be updated to assume something closer to e.g. Debian's take on version number syntax?

Alternatively, is there a way to hint apkg what version to expect so it doesn't have to parse the source archive filename?