I built my last OTSM drivers in early 2017 (focused on momentary switches now) and couldn’t find any notes :person_facepalming: so had to open a S2+ triple with this driver and see what I’ve used:

Found 2 added ordinary 100uF X5R ceramic caps, connected to GND and Vcc of mcu. I measured them about 160 uf together. The driver is a BLF X6 with Attiny25. But beware the BLF X6, there was a batch with reprogramming locked by fuse. I don’t know if Banggood made a change afterwards, I haven’t bought this driver since that time.
Btw - why do you think you can’t use the Attiny85?