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There are diodeless (no matrix) split keyboards (https://www.reddit.com/r/ErgoMechKeyboards/comments/1dh9o8k/...) like Cantor: https://github.com/diepala/cantor .

They use chips similar to that one: XIAO ESP32S3 nRF52840 Sense Plus - wireless, energy efficient, with 20 pins GPIO or more - one pin for one key - https://thepihut.com/products/xiao-nrf52840-sense-plus (there was an option of 16 pins extra using expander https://wiki.seeedstudio.com/io_expander_for_xiao/ - which is not made anymore, but you can use same chip MCP23017 to get that effect https://www.youtube.com/watch?v=lq6jbXaX4oQ https://www.youtube.com/watch?v=74DgM2nAeLo , up to 128 I/O pins: https://resinchemtech.blogspot.com/2023/10/IO-expander.html - in that case - 36 simultaneous inputs by hand) - and with Hall sensor keys or similar we are soon talking about _easy_ having ~40+

.. simultaneus muiltiple ANALOG inputs in "keyboards" - like in Mitt https://www.youtube.com/watch?v=Oj7HfcdJhi8 - or XBOX Controller Mods: Analog WASD Gaming Keyboard https://www.youtube.com/watch?v=gEwDImE0DU4 .

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Edit: nRF52840 chip can have 12 Analog Inputs, ESP32S3 20 - e.g. ESP32-S3-WROOM-1 - but XIAO ESP32S3 and XIAO nRF52840 have 6 only, there are others with more pins (AFAIR up to ~128, not all analog) but more functions too - what's overkill regarding price and energy waste - not so cool. (BTW. of A beginner tries PCB assembly (2020) https://news.ycombinator.com/item?id=32549736 )