I did not realize that a remote console over a serial port was possible by default in linux. I was assuming that I would have to write some special program to read and write from a serial line, and fire your wtfplayer accordingly. This is great! Makes my task much easier.
I am waiting on an RS232 cable to come via allegro.pl to test all of this. In the meantime, I did some reading and also noticed this article on kernal.org:
Linux Serial Console — The Linux Kernel documentation
In addition to RS232, it mentions a serial console via "ttyUSB0". Do you think this kernel parameter would work on your wtfplay-live distribution? If not, RS232 is good enough. However, my thought is that if it is possible, USB would be superior on 2 fronts:
1. In 2021, USB ports are pretty much universal on motherboards, and the cables are more common. RS232 is far less common.
2. According to wikipedia, the RS232 spec has "Single-ended signaling referred to a common signal ground", which "limits the noise immunity." If I read that sentence right, I am guessing that more electronic noise could get into the system with this connection, then presumably USB. Though, this is pure speculation, as I am no expert in electronics. I am assuming that wtfplay sounds very good because the minimal system acheives lower jitter.
Also, I absolutely love the fact that your system is only 24MB! Well done!