The tab icon isn't working reliably for Web Access in some browsers. In IE and Edge (tested on Windows 10) the icon is visible during login, but not when the session is active. This was tested with eudemo. On my 4.10.1post system I'm not even getting an icon during the login page. Not sure if it's because it is a newer version, or if it's something else (e.g. the self signed cert).
Needs to be retested with the new Edge browser.
I tested this on Microsoft Edge Version 95.0.1020.53 on Windows 10. ThinLinc server Version 4.13.0post (build 2350) on Ubuntu 20.04. The icon is working both for the login page and when the session is active. Since we are dropping IE and old Edge support as of bug 7550, this bug can be closed.