I have SdrGlut running in native M1 mode on the new M1 MacBook pro. I supports the hackRF, lime, and rtl devices. I looked for the SDRplay drivers, but as you said they are not available in source form. If the drives were written in C, it would be a simple recompile. Perhaps, they are written in ASM – then it would be a lot more work – people do not realize that compliers stink – ASM is often times five times faster.