Okay, to try to narrow this down a bit, I setup a very large AWS Fedora 33 instance and built chromium packages, then installed them into a second Fedora Rawhide instance.
As before, these packages work fine. (This is our baseline)
Next, I updated glibc (and JUST glibc, glibc-common, glibc-devel, glibc-headers, glibc-langpack-en) from Rawhide on the Fedora 33 instance and built the chromium package again. This build, when installed into Fedora Rawhide, exhibits the text rendering issue.
This makes me very suspicious of something in glibc between 2.32 (Fedora 33) and 2.32.9000 (rawhide), but I'm not sure where to look from here. Any ideas?
~spot