[VitalKoshalew]

I have actually came up with a similar setup (accidentally with the same typewriter model so I've gratefully used keycode table created by the author of this article). I didn't replace the keyboard though. My chip mod is working in parallel to the existing keyboard. I'm using RP2040 (Raspberry Pi Pico clone) with multiple assembler-programmed PIO state machines doing great job intercepting keyboard signals as well as emulating them in real time.

I've also coupled it with a 1975 vintage IMSAI 8080 computer emulation running Z80pack[2] on a Raspberry Pi 4 with a touchscreen attached.

Here is a short video[1] of my setup running XYBasic.

1. https://vimeo.com/801331428 2. https://www.autometer.de/unix4fun/z80pack/