This is awesome. I was recently reminded of the OpenSPC tool, and remembered how useful it was to pretty much perfectly rip the audio samples (with their loop points!) and use them in my favourite music tracker (which also works with .it files). Thank you so much for bringing this to modern systems. I'm very happy I can run this on my Linux system, even if it's not perfect and notes are dropped.

That said, besides the known bugs, I think there is still room for improvement for the sample dumping! The samples themselves are dumped perfectly, but it's dumping them as regular samples rather than instruments. If you dump them as instruments, you get the power of adding effects to the samples, which allows for emulation of the SPC's echo and reverb effects.
There's a limit of 200 patterns in IT file format, anybody here suggest a better format?
Well, the newest tracker-type format I can think of is .mptm, and that's actually more or less just like the .it format except extended as far as I'm aware. One possibly beneficial improvement is that it allows for multiple pattern sequences (basically meaning more than 200 patterns). Might be worth looking into.
I also have a question, or rather, a point of discussion:
How come it polls the SPC file a whole bunch of times per second and creates soooo many rows at a super high tempo that don't seem to fit in an accurate, regular timing in the .it file? In this one file I noticed that one beat takes 17 rows, which is already an odd number. Then the next beat after it takes 18 rows, and then the one after THAT is 17 rows again, all while 16 rows would have made a lot more sense because you get a perfectly steady rhythm on beats that are all equal length (and preferably a power of 2). I guess it has something to do with rounding, but does it really have to round things so inconsistently? Is there anything that can be done to fix this, like figuring out what the bpm and most regular beat/measure distance of the song is before dumping it into the IT? This would also fix any potential "200 patterns is not enough" issues because the song can be accurately fit in less rows.
But anyway! Thanks a ton for this effort. I'd be more than happy myself if just the sample export side of things gets explored for improvement, but that's not all the tool sets out to do, right?