I use emulators that play directly from (.iso) or (.img) files, however as you probably know, most ROMs are downloaded as archives.
Do you backup your ROMs in their downloaded archived format? Or as uncompressed files?
I searched for "YTDLnis" inside my F-Droid client (Droid-ify) and it worked.
I searched for "YTDLnis" inside my F-Droid client (Droid-ify) and it worked.