Optical Key Switch
Optical key switch became popular around 2016, due to the Bloody B840 Optical Switch Keyboard using the βBloody LK Optic 2 switchβ.
Optical switch is great because it does not need metal contact. Meaning, no wear, last longer, and easier to be water resistant.

Optical Switch Manufactures

Optical Key Switch keyboards
There are a lot. Here's a few example.
Key Switch Topic
- Key Switch Mechanisms
-
Rubber Dome -
Scissor Switch -
Cherry MX Switches - Noise Comparison
Buckling Spring- Kaihua Kailh Switch
- Kailh BOX Switch
-
Kailh Choc Switch
Romer-G Switch
Topre Switch
Niz Switch-
Varmilo EC
Optical Switch- XMIT Hall Effect Switch
ALPS Switch- Old Key Switches
- Mechanical Keyboard and RSI