the link posted is probably well known. This is my main source where I get news about upcoming games for old computers and consoles. From time to time I also check itch.io and crawl the known tags for new games.
I will generally take every source for any vintage system but I'm especially interested in Amiga, C64, all 8-Bit Ataris, NES, Master System, Gameboy and Torbografx-16.