Since we are in the fediverse, I think it would be convenient to have a fediverse-wide resolvable fediverse URI scheme, that would look like so:
fediverse://
edit: Found a relevant FEP: https://codeberg.org/fediverse/fep/src/branch/main/fep/07d7/fep-07d7.md
Upside down, as the other comment says. It should rather be
forum://or similar, i.e. a generic self-explanatory term for the type of data. The branded networks like this one would then follow the standard in order to display properly.