TL;DR: How to turn on Remote Desktop safely on Windows 11

The fix only. No explanation, no diagnosis. Read the full article if any of this does not match what you are seeing.

1. Host must be Pro, Enterprise, Education or Server (Home cannot host). Settings > System > Remote Desktop: turn Enable Remote Desktop On and Confirm, then tick the Network Level Authentication option.
2. Remote Desktop users > Add only the accounts that need access. Administrators can connect already.
3. Limit the firewall rule to your management subnet (use your own range):

Set-NetFirewallRule -DisplayGroup "Remote Desktop" -RemoteAddress 192.168.10.0/24

4. From a PC inside that range, confirm the port answers:

Test-NetConnection -ComputerName PC-NAME -CommonTCPPort RDP

5. Switch it off again when you are finished (Settings toggle Off, or fDenyTSConnections = 1 and Disable-NetFirewallRule -DisplayGroup "Remote Desktop").

Never forward TCP 3389 from the internet. Use a VPN or a Remote Desktop Gateway.

A scope that does not include your own PC locks you out of the rule you just made.

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