Out of necessity for my tournaments, I built bracket software that runs in a terminal (RaspberryPi or bash/python) that doesn't require network connectivity or a mouse. It's all keyboard. It supports double byes and byes, and lets me set seedings and query IFPA for rankings if I do have a wifi connection. I've built brackets from 8 to 24 people with it and have people walk up and sign up to register. It lets me record scores per game/match and has limited 'arena' support. It has the capability of tracking match times, as well, and dumps the results into the IFPA CSV format.
I could make this available for free/cheap but doubt that I want to make it open-source. If this sounds useful, rather than dumping some binaries somewhere, I'd rather understand what the needs of your tournament are and determine if it meets your needs and I could test some scenarios to check that it would work for you.
And I'm not the Brian@IFPA. just another Brian who sees an opportunity to give back what I've spent probably too much time working on.