I use a computer with the MediaTek MT7921e adapter and it is a real pain to get working. Here's a bunch of problems and how I fixed them:
First off, go into Device Drivers -> Network device support -> wireless lan when configuring your kernel and enable MT7921E support.
Second off, sometimes the driver won't load. So when you do start your system, run modprobe mt7921e!
Thirdly, sometimes bluetooth will just not work. This probably has to do with dual-booting Windows. Random other pages on the internet say that turning off your computer, unplugging it, and leaving it off for several minutes, then booting directly into Gentoo fixes the problem. this works (sort of) reliably for me.
Another possible fix for the Bluetooth issue is bumping your kernel version to 5.16 or above. This doesn't work as of kernel version 6.0.8 for me, so I don't believe this is accurate.
Finally, sometimes WiFi will randomly stop working. My computer recently had a kernel panic or something while running MATLAB, causing the WiFi to get borked. I solved this by turning off the computer, unplugging it, and leaving it off for several minutes.
Remember that restarting while plugged in does not fix the problem, as the MT7921e remains in whatever state Windows put it in. Removing the AC power causes the adapter to lose power and reset.
If it's not clear from reading this, the MT7921e is a low-quality adapter with many problems and you should consider avoiding buying a computer with it inside.