I'm trying to upload to an ATTiny841. I have lots of experience with the ATTiny84 and have no problems there, but the 841 gives me:
avrdude: AVR Part "attiny841" not found.
I'm running Arduino 1.8.4, avrdude 6.3, and ATTinyCore 1.1.5 (Konde).
I see some discussion of this online, but it all seems old and seems to suggest that up-to-date avrdude should support ATTiny841.