I’m currently running Safari Version 14.1 (166220.127.116.11.6) on macOS 11.3.1 (20E241) and since about last week, our app (https://app.shadowmap.org) seems to run ridiculously slow on this config. I am pretty convinced it is caused by the latest update for Safari.
Other browsers including Brave and Firefox on the same machine/OS run still fine. Safari on iOS behaves as well as ever too.
Does anyone have infos about what happened to Safari? Maybe has an idea how to compensate/fix the performance drop?