I've been working mostly on Arduino libraries lately and have made a few also run on the Raspberry Pi. I recently acquired a RPi4 and decided to port some more code back to the RPI. I just ported my ss_oled and BitBang_I2C libraries so that the RPI can now control any number of simultaneous OLED displays (of all types) on both hardware I2C and virtual I2C buses (aka any GPIO pins). Clock lines (SCL) can be shared, so even if all of your displays use the same address (e.g. 0x3c), you can control N simultaneous displays with N+1 GPIO lines.
Here are the github repos:
Go to the repo's linux directory and run 'make' to create the library, then 'make -f make_samples' to build the same programs