Need help on building retroarch on Pi 4 raspbian

I’ve read many post Finally, i did installed retroach on my pi4 with raspbian os/img. (yer, not lakka)

I am now struggling how to find the core and install them i’ve read

it taught me how to use libretro-super fetch and build a core i also learnt goto some github and git clone that path , Make that file myself

I have the following problem I want to try flycast, ppsspp, dolphin, but on those github , i can’t see a file called make.libretro or if i just follow the guide on the link above, i will reach an error and i can’t have that file Why? is that some emulator core is not available to linux? But as far as i know , someone using lakka retroarch can sucessfully playing ppsspp / flycast in their pi 4.

Many thanks