PWM output while using I2C with the ATTiny library I've noticed that when using the USI interface on the ATTiny to send I2C via the methods from "Wire.h" with the ATTiny Arduino implementation included from the library manager (ATTinyCore), while analogWrite PWM on PB4 (Arduino pin 4, physical pin 3) works OK, it seems attempting to use it on PB1 (Arduino pin 1, physical pin 6) behaves erratically or hangs the processor.

Is this expected behavior, and is there a workaround? With the SDA line on PWM pin 0, physical pin 5 if that's the case it means when using the hardware USI to do I2C communications, I'm down to a single hardware PWM output, which is kind of a bummer.
This is normal.

Timer0 is used as the clock source for the USI. It's the only internal clock source that can be used. The only other option is to use "software polled" mode where it's up to the sketch (or support library) to manually create the clock signal (less than desirable) by setting a bit in a register at the right time.

So you can only use Timer1 for your own (PWM) purposes while using the USI.