Awesome.
Thanks!
-aldo
you asked where to put these files and nobody answered you. i had the same question and i struggled for 3 hours trying to figure out where to put the new /attiny directory and its files. for some reasons that can only be attributed to satan taking over arduino, the attiny zip file you download contains the board.txt (which you have to modify).... but this file needs to be moved from the /attiny main directory to the /attiny/variants directory. basically, you download the files and the directory structure, but it's wrong from the start and nobody tells you that you have to 1) put the new attiny main directory into the /documents/arduino directory, but you also have to create a new directory called /documents/arduino/hardware, move the /attiny to the /documents/arduino/hardware directory AND move the board.txt file from the /attiny directory to the /attiny/variants directory. and NODBODY tells you any of that. worse: the boards.txt file COULD have been in the attiny/variants right off the bat, but noooooo.... you have to figure it out by yourself. it's like these guys are making it difficult on purpose.
If you're using a modern IDE, my ATTiny core (which supports the ATTiny24, as well as just about every ATtiny processor that's interesting with Arduino) supports installation via board manager, so you don't need to copy or rename anything - it's all done through the GUI ( see install instructions for my core ATTinyCore/Installation.md at OldMaster---DO-NOT-SUBMIT-PRs-here-Use-2.0.0-dev · SpenceKonde/ATTinyCore · GitHub )
boards.txt should not be located in the attiny/variants directory - the IDE won't see it there. I would expect moving it there to prevent whatever core you're using from working.
Instructions detailing the process for manual installation as you did are widely described - the only thing that isn't is moving boards.txt into variants, which you shouldn't have to do.