with the beta4 I can't program an ATtiny85 anymore, the selected programmer Arduino as ISP isn't accepted:
Upload error: Error: 2 UNKNOWN: a programmer is required to upload for this board
A Mega2560 works fine.
In Arduino 1.8.13 I have no problems programming the Tiny, so the ATtinyCore v1.5.2 seems to work properly.
Here is the list of my additional board managers: