OK, I couldn't find any specific documentation just floating around about group links. It appears that the base64 value is specific to the group and is only exposed through the link. I didn't see any way to munge the "signal.me" domain and fix it again. So for groups Twitter/X seems to have won.
No. Signal groups are advertised with signal.group URLs.
Which, it is worth noting, are not blocked. I checked.
OK, I couldn't find any specific documentation just floating around about group links. It appears that the base64 value is specific to the group and is only exposed through the link. I didn't see any way to munge the "signal.me" domain and fix it again. So for groups Twitter/X seems to have won.