Since Firefox version 114, the WebUI no longer loads. Just an empty, white, page. Source shows:
<div id="noload" style="position:fixed; top:0px; height:100%; left:0px; width:100%; background:white; padding:40px; z-index: 9999;">
<br>
<div>
Your system was unable to load Resilio Sync properly.
For information on how to fix this issue, please see the
<a href="https://helpfiles.resilio.com/helpcenter1">Sync Knowledge Base</a>.
</div>
Firefox ESR 102 works fine. As well as Chromium based browsers. Tested from Windows and Debian Flatpak. Firefox ESR portable on Windows. Resilio Sync running as a docker container on Linux, linuxserver.io builds. Resilio Sync Home Version 2.7.3 (1381).