> ARM has added both pointer authentication codes and memory tagging extensions to their ISA, from (I think) ARMv8.5-A. Apple are the only ones to implement silicon that supports PAC that anyone can buy today but a) this will change fast and b) I might've missed something else.

I'm not aware of other generally available chips with pointer authentication. The Qualcomm Snapdragon 8cx Gen 3 supposedly support PA. The Lenovo ThinkPad X13s supposedly contains it, but when will it actually be commercially available is anyone's guess.

Also, I think it's ARMv8.3.