I wonder to know why we can´t have a RA on Atari 5200 , is just a little curious because , we have in 2600 and 7800 even in the jaguar and lynx but , why we not have in 5200? can someone explain to me please , thanks
I guess Atari 5200 emulation in RetroArch was quite rudimentary up to this point. The only core capable of doing this was Atari800, and there were some issues with implementing cheevos in it. You can find the details in RetroAchievements docs:
But now there is a new core dedicated solely to A5200, so maybe this will open new possibilities.