Conservatively though, another answer could be when not considering subset registers as distinct:

16 GP

2 state (flags + IP)

6 seg

4 TRs

11 control

32 ZMM0-31 (repurposes 8 FPU GP regs)

1 MXCSR

6 FPU state

28 important MSRs

7 bounds

6 debug

8 masks

8 CET

10 FRED

=========

145 total

And don't forget another 10-20 for the local APIC.

"The answer" depends upon the purpose and a specific set of optional extensions. Function call, task switching between processes in an OS, and emulation virtual machine process state have different requirements and expectations. YMMV.

Here's a good list for reference: https://sandpile.org/x86/initial.htm