We're upgrading to Windows 10, using SD 11.2 (I know, it's old, sorry). Instructed users to use IE11. Most are having no issues at all. Some users have extreme slowness (about 10-12 seconds) when opening up any new form; for example the new Incident/Change form, or any ticket. Navigating around is speedy, right up until a new form is called. The "avoid popups" setting addresses this performance issue, but most people seem to prefer to take the performance hit. In general, this seems very similar to another post where people noted performance issues with Edge.
Service Desk is in the "Local Intranet" zone, "Enable Protected Mode" turned off, with Compatibility View on. I can't seem to recreate the issue myself, though there are a fair number of users who are experiencing the slowness.