I'm having wifi issue with our m2 mac mini as well.
My internet plan is 150 and I'm getting about 60Mbps download 30~35Mbps upload, sometimes worth.
I get 150~170 Mbps, both upload and download, on all other devices on the same wifi network including two iPhone 13s, 2 iPads (m1 ipad pro & ipad gen 6), and my work issued Thinkpad x13 gen 2 amd. Even 10 years old late 2012 MBP had no issue getting the 150 up/down.
We sold 10 year old late 2012 MBP to upgrade to this mini, and it's really disappointing to see this wifi issue. Especially when internet/wifi is almost necessary, key function in this age. Our newest tech purchase has the slowest wifi.
And, all this network setting/troubleshooting mentioned in this thread seem very techinical and an average consumer shouldn't need to worry about this in my opinion.
Is this a hardware issue or something that software update can fix? I need to make a decision to return this or not... and pretty soon.