Polari is sloooooow
Since recently, the Polari become totally unusable. I would date it back to the time when it started to display URL previews. Since that day, it is almost unusable. It takes ages to send any message, it takes age to receive message. The popup in gnome reacts almost instantaneously, but Polari does not show anything ...
$ rpm -q polari
polari-3.36.1-1.fc33.x86_64