I spent a while figuring this one out. Here is what I did to render it [Solved] on my Dad's new Sonoma iMac. (BTW: I caused this problem in the first place by enabling his nfsd service, then adding and tagging the snapshot as bootable)
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Boot into recovery mode, open the terminal and disable SIP
csrutil disable
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Reboot at this point back into Recovery mode and this time open up DiskUtil