Hi,
I can't believe I didn't mention it here :picard: (according to the forum's search, at least).
Because I couldn't find an IRC channel about retro game development (people prefer discord or telegram, apparently), I decided to start my my own! Is not CPC exclusive, but it is hard to find enough people on a single system that also want to use IRC :D
It is the #retrogamedev channel in libera.chat; there is a website: https://www.usebox.net/retrogamedev/
The channel has been operating for over a year now and even there's the occasional chat about retro gamedev (even CPC; for example
@PulkoMandy is there and has shared a few times their adventures porting Smalltalk to the CPC).
Everybody is welcome to join the channel and idle with the rest of us :D
Cheers!