Issues with M2 Mac mini thunderbolt and wifi

Dump the cable and get an HDMI certified and well shielded cable. Alternatively, if your display has DisplayPort inputs, use a VESA certified USB-C to DisplayPort cable.

Poorly shielded display cables can spew radio frequency signals at very high frequencies. Even if the shielding is partially broken at the connector end or the connector is not making good connection to the device ground it will spew interfering signals.

I agree with the others about using poorly shielded cables and devices.

I would also like to add that the arrangement and location of poorly shielded cables and devices, can have a big effect on both Wi-Fi and Bluetooth reception. see > Resolve Wi-Fi and Bluetooth issues caused by wireless interference - Apple Support

I concur to use ports aimed for specific tasks: HDMI to HDMI, and if feasible, since the mini is aimed to be a desktop, go with a wired connexion (ethernet). Not only should this improve stability, but in many instances you will access the real internet speed you pay your ISP for. (In my case, i get almost twice the speed i get with wifi by using ethernet - which indeed is what i pay for)

Looks like a noisy display and/or bad HDMI cable. How long is the cable?

Hi,

Officially you can connect 4 displays on your Mac mini, so you can connect 2 displays without any trouble.

I think you should contact Apple Support to tell then the circumstance you face with now.

Official Apple Support

I get 1300 Mbps on my WiFi…