I've had this problem for about a month now. The last few thunderbird updates have been performing very slow on my system. I frequently get the 'wait or force quit' dialog popups when trying to use thunderbird. When viewing emails with HTML content, it often has long pauses where nothing happens and the UI is unresponsible. I do have multiple email accounts, a lot of email (multiple folders with 20K+), and irc open. CPU and memory utilization are fairly low on the PC. It's a desktop with a 11900k + 32GB RAM + nvme m.2 pcie gen 3 ssd + intel arc a750. I'm noticing issues on wired (via powerline) or wireless (802.11ax)