I use OperaGX and before the most recent update LVL3 (core: 79.0.4143.73) I could rename tabs no issues, but now when I click rename tab (just on OperaGX tabs) the rename window box will flash in the center, and then vanish. Going to try to roll back the update but not sure if it'll work or not 
Update/Edit:
Everything after version 78.0.4093.214 has this issue but was able to roll back to 78.0.4093.214 and renaming tabs works again.