Your issue is not that OPLS and AMBER aren’t directly compatible with GROMACS (which they are), but that you’re mixing the two, which is generally a bad idea. You have a bunch of OPLS atomtypes in your [ atomtypes ] directive, and then you’re adding AMBER-style atomtypes in the [ atoms ] directive.
E.g., if you’re using OPLS, the type part of your atom definition should be something like opls_XXX. Both LigParGen and acpype should generate .top and .itp files that are intended to be used together, so just deciding for one of them should do the trick.