use Centos Stream instead of Fedora for bindists?
Motivation
I think it is great that ghc is releasing bindists built on Fedora. On the other hand from the point of view of API/ABI, I think RHEL major versions seem a better baseline to follow. (eg Fedora 33 is closer to RHEL 9 (based on Fedora 34) than RHEL 8 (based on Fedora 28-29 I think)). So while I am not completely sure how Fedora 33 was chosen (was it because it was the newest EOL fedora release at the time??), and Centos Stream is still being actively maintained, since Red Hat basically guarantees stable library ABIs (sonames) for the whole lifetime of a RHEL/Centos Stream major version, I feel it would make more sense to use it over Fedora (as much as it pleases me to see Fedora there). Centos Stream 8 will be supported until 2024, by which time it would probably make sense to have moved to Centos Stream 9 anyway (or you could also build now against both 8 and 9 if you wanted to).
Anyway I just wanted to put this idea to the ghc maintainers for their thoughts. Another option could be to use the free RHEL UBI container image instead, which is even more stable and longer maintained than Centos Stream (even though its updates have been through basic QA, and it's maintained for 5 years).
The point is really just that if you follow RHEL or Centos Stream major versions then you don't need to worry about which version of Fedora Linux to choose from (there's a new Fedora release every 6 months). This would also be closer to the approach of the Debian major versions. RHEL major releases are now happening on a 3 year cycle.
Or you could just choose to base on the Fedora version which is the base for the RHEL release. Arguably that is what you have been doing (off-by-one) with Fedora 27 and 33. :-) I could certainly provide input for future Fedora bumps. It's just that some users got thrown by ghc's switch to F33 (roughly like the major jump from RHEL 8 to 9) due to the glibc version bump (maybe ghcup and stack have been adjusted already by now to compensate for this?).
While ghc is still providing a build on Centos 7 (EL 7), with the jump from Fedora 27 to 33 you essentially moved roughly from RHEL (EL) 8 to 9: I think it would make more sense to provide both EL 8 and EL 9, though there are still many EL 7 systems around, there are also still rather more EL 8 systems than EL 9 at present (that will start to change more as 7 draws nearer to EOL) - though F33 is probably okay for recent Linux distro versions.
(Sorry this got rather long - perhaps I should do a tl;dr summary or shorten it...:)