Edit: oops, I replied without checking for thread updates first. Glad it’s working!
Fuses are still a thing, but most of the settings can be done in firmware and don’t need manually setting if fuses. BOD (brown out detection) is an exception, but that wouldn’t affect ramp speed.
My thread here has some info on doing fuses with pymcuprog.
Could you try my hex file here I would check your tk-attiny.h file too. At some point I changed between 5 MHz clock and 10 MHz, so it’s possible that it might be using an old setting.