Hall effect switches have existed in keyboards for a long time [1].
I don't think there are many of them being produced nowadays though, but there's at least one new Chinese Hall effect keyboard that came out a few years ago [2].
Wooting also has a Hall effect switch [3].
You can't buy any keyboards with it yet but you can pre-order one at least [4].
[1] https://deskthority.net/wiki/Keystroke_sensing#Hall_effect
[2] https://geekhack.org/index.php?topic=84525.0
[3] https://blog.wooting.nl/introducing-the-lekker-switch/
[4] https://wooting.io/wooting_two_lekker_pre_order
