Yes, avx512 shows up in cpuinfo, although with the spec consisting of many optional modules and not being a monolithic thing, each supported part will show up separately.
My 7800X3D has these avx512 flags:
avx512f avx512dq avx512ifma avx512cd avx512bw avx512vl avx512_bf16 avx512vbmi avx512_vbmi2 avx512_vnni avx512_bitalg avx512_vpopcntdq
yes, zen4 is the ryzen 7xxx ans onwards. I think they will change the naming scheme again after the 9xxxs now though.
In my case my 5xxx cpu shows avx2 (256bit) in /proc/cpuinfo, I assume you will find avx512 there if you have it.
Also apparently there are mobile and server cpus with 7xxx names that are zen3. It is a mess certainly.
Yes, avx512 shows up in cpuinfo, although with the spec consisting of many optional modules and not being a monolithic thing, each supported part will show up separately.
My 7800X3D has these avx512 flags:
avx512f avx512dq avx512ifma avx512cd avx512bw avx512vl avx512_bf16 avx512vbmi avx512_vbmi2 avx512_vnni avx512_bitalg avx512_vpopcntdq