I find the same issue. At least I can have a custom alarm tone...
Read my post above, ot worked for me.
Yes, I moved the files into the ring tone folder using my PC, although I've not converted them to m4r format. These same files worked perfectly well for me on previous builds.
Actually when I was transferring my ringtone to the ringtones folder, PC asked me If I wanted to convert the file, I choose yes and it converted my Godfather guitar.m4r into .wma file
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