@voljega: Nice job getting this to work.
I am pretty sure some of the whdload .lha files often have amiga filenames that can only be uncompressed correctly in an Amiga filesystem.
So, ideally, I think the emulator should take the .lha file as a launch argument and automatically uncompress into a .hdf file to ensure filenames are all correct. No need for .uae file then. It could be read automatically for custom config if it exists, but that's it. This was already solved by FS-UAE.
I also think that a virtual keyboard, analog stick mouse control and gamepad control of the menu are necessary for this to become usable in a typical Pi setting in front of the TV.
I don't think many users have a keyboard and mouse connected to their Pi. It seems the spirit of recalbox is very much to have everything controllable with a gamepad. I for sure don't have a keyboard and mouse connected, that's really the last thing I want when I am in front of my TV.
BTW: Shameless plug, but for anyone who has a cfw VitaTV, UAE4All2 is also a nice alternative for Amiga emulation on the TV. It already has a virtual keyboard, analog joystick mouse, custom control configs for four controllers, etc. etc.