Originally Posted by gulliver
LIBS/68040.library (680x0.library exists but see note no. 1)
This is by design, it is more compatible this way!
AmigaOS setpatch and/or 680*0.libraries can't be aros compatible, they do undocumented patching and aros has built-in 68040 and 68060 FPU support. Simple Enforcer-like MMU debugging code is also ROM built-in (can be enabled very early in boot), it also would not be AOS 680*0 library compatible.
AROS actually has extra code to force AOS setpatch to become no-op and also not to load 68040 or 68060 library which would only cause instant crash
AROS library is only needed to enable copyback (sets up MMU tables) and missing instruction emulation.