There is a Attinycore installation bug workaround described here for version 2 of the IDE
And for those like me that use the old IDE V1 (portable) there is different writeup of the workaround
There is a Attinycore installation bug workaround described here for version 2 of the IDE
And for those like me that use the old IDE V1 (portable) there is different writeup of the workaround