You got that far so I assume you have some experience, but anyway…
Using the standard Software List method the bios is defined by the name of the folder the roms are in. So apple2, apple2p, appl2e would be the folder name. (And the bios of the same name needs to be in the same folder.)
Try the same method using the “apple2p”. (I have the same issue with the “apple2”.) It uses the same romset so it makes no real difference. Also make sure to use the “apple2_flop_clcracked” SL roms.
The MAMEDev page says the main difference between the appe2 and appl2p is the ability to autoboot. I am assuming we would need an autoboot command for the apple2, which is inconvenient unless all the executables have the same name.