It shouldn’t be terribly difficult to source a Sun Rhyno XL rim.
Tire choice would be a determining factor. I think most of the non-Asian world is under the impression that 26” is the easiest to find tire size in most Asian/Pacific countries. That sucks that you’re finding it difficult to source them.
It’s nice having identical sized rims so you can stock yourself up on one size of tires for emergencies like sidewall shreds.
Mullet builds really are for people with disposable money to do with one of their ten or twenty bikes as a silly side project.