So after some playtesting, I’m 100% confident I’ve found a work around for those affected by the guild UI/guild chat interface bug.
The bug is on Blizzard’s end, but that does not mean we can’t fix it from our end.
For some odd reason, being gkicked and re-ginvited seems to fix the issue. This includes for those who are rank 1 in their guilds. (You’ll have to find someone you trust to become guild master for a second so they can gkick you and then re-invite you and re-promote you)
to access the guild interface tab with this bug active, simply use /groster, which will open the old guild interface.
I believe data fiags are erroneously being set to NOT show you guild chat or guild UI. this work around resets the flag, allowing you once again to access and use the guild interface and guild chat.
This work around does persist, compared to the gleave method.
After killing my game, restarting my computer, etc, the work around persists.