RFT vs non-RFT is the least of your concern whether you're wanting to do this because of tread life, comfort, or supply availability. you want the handling characteristics of
all tires to be the same, otherwise you are at the mercy of the 'least' performing tires. if their handling characteristics are similar, then you could be ok, but mixing tire brands/types is typically not recommended
i actually did this, but it was only momentary until the correct tire was delivered. one of the RFT on my wife's G30 blew out, but the dealership didn't have one in stock. however, they did have a different brand non-RFT of same size and performance that I let them mount. we didn't experience any handling or transfer case issues driving like that for 2 weeks until the replacement RFT was mounted.
there's several threads on this subject, most recently here where one guy is having a difficult time finding a winter setup, and someone posted maybe doing a mixed tire setup (though he also disclaimed it's not recommended):
https://www.bimmerpost.com/forums/sh...php?p=29226151
you gotta do what you gotta do in these times. good luck!