I have tried every fix I've found with mixed success, meaning they work temporarily at best. Haven't found a permanent fix. As it stands now I lose my internet usually for 10 or 15 minutes at a time.
Here is a page for downloading a driver. Maybe an older driver will help you. Sorry I couldn't be of more help.
https://oemdrivers.com/network-mediatek-mt7921-wireless-lan-driver