Youtube bug

Lenovo Legion, Windows 11. After CCleaner (including registry clean) Discord, YouTube and downloads broke.

Now:
– google.com loads, other sites spin forever / YouTube homepage is grey placeholders
– downloaded ZIP files often corrupt
– phone on the same networks (guest Wi-Fi and mobile data) plays YouTube fine
– laptop fails on both guest Wi-Fi and phone hotspot (Wi-Fi)
– clean Windows 11 reinstall (delete everything) did not fix it
– DNS 1.1.1.1 / 8.8.8.8 did not help

Wi-Fi adapter: MediaTek MT7921.

Is this the MediaTek driver? I have not tested USB tethering by cable yet.