On AArch64 the return address lives in a register, not on the stack — until a non-leaf function saves it. Build the ARM ret2win in a lab and see where the saved link register sits.
Pointer authentication signs return addresses so a forged one faults; BTI forces indirect branches onto landing pads. How both work, how to enable and verify them, and their limits.
AArch64 gadgets end in ret, which branches to x30 — so the chain is threaded through the link register with ldp gadgets. Build a system("/bin/sh") chain, then watch PAC and BTI break it.