I can download megaTinyCore and MicroCore but when I try to Install 1.5.2 (current) version, I get the following error on the Board Manager dialog screen:
I checked the issue trackers of the various repositories that might be affected and didn't find any existing reports (there are some about the SSL certificate of the site having expired, but that was a separate problem which had been resolved before the time this new problem started).
If we had a copy of the micronucleus-cli-2.5-azd1b-i686-mingw32.zip file, I could provide instructions for a workaround to the problem. Unfortunately I don't have a copy of that file though. Maybe one of the other forum helpers do.
For the forum helpers, you should have it on your computer if you ever used Arduino Boards Manager to install ATTinyCore version 1.5.2 on a Windows 32-bit computer. If you find it, you can share it here by adding it as an attachment to a reply. We have the checksum for the file so I can verify it is legit.
ⓘ Note that the AppData folder is hidden by default in "File Explorer". You can make it visible by opening the "View" menu, then checking the box next to "☐ Hidden items".
It looks like the azduino.com website is back online now! Please try installing ATTinyCore again just as you did before @happymac85. Hopefully it will work this time.