Additional meeting and call-related features and issues within Microsoft Teams for business
The best tool to use is Microsoft's Quick Assist, built in to windows 10. You will be surprised how good it is. Can see both screens, initiate task manager and you can use the UAC.
What I suggest is to make some changes in your GPO on how the UAC presents itself but does not turn it off.
Computer Configuration/Windows Settings/Security Settings//Local Policies/Security Options
| Policy | Setting |
|---|---|
| User Account Control: Allow UIAccess applications to prompt for elevation without using the secure desktop | Enabled |
| User Account Control: Switch to the secure desktop when prompting for elevation | Disabled |
These will stop the black screen but give the prompt, and yes you can enter your credentials with no problems