you are on facebook? "The Amiga RetroPie WHDLoad Group"? Then: https://www.facebook.com/groups/AmigaRetroPieWHDLoad/permalink/2062582597303082/ (Dom is HoraceAndTheSpider @ Github; Midwan is also in this group). Its an " Experimental Amiberry Binary" (rpi3 i think; "your" 2.1-Binary was for rpi2 - why not 3? You have an rpi2 or "compatibility"?) ... but you can compile your own from the Horace-Fork?! I haven't done any compiling by myself yet;) ... if the Menu "crash" to ES -> you need some icons @ data/ (controller(s?).png and quickstart.ico).
Or "directly": http://www.ultimateamiga.co.uk/HostedProjects/RetroPieAmiga/downloads/ -> at the bottom "amiberry" is the binary.
Here is the thread @ Github: https://github.com/midwan/amiberry/issues/114... there you can find "my" RetroArch-Config (post from Horace) - as example.
I hope I have a little time to deal with this today. I have only tried ECS games so far... I don't know how AGA (1200) reacts yet. Isn't that supposed to work for CD32?
WHDLoad should work (Horace is Admin from the WHDLoad-Group...) ... no experience with this (i like *.adf G ... mhhh .... G)