Hello, I have exactly same issue as yourself, both on usb live installer and on Installed Ubuntu I get this MCE:
[ 0.067525] mce: [Hardware Error]: CPU 0: Machine Check: 0 Bank 6: ee2000000040110a
[ 0.067527] mce: [Hardware Error]: TSC 0 ADDR fef1e680 MISC 43880004086
[ 0.067530] mce: [Hardware Error]: Processor 0:a0655 TIME 1622366143 SOCKET 0 APIC 0 microcode e2
Is exactly as yours, same address "ADDR fef1e680".
Ubuntu works fine so I think is a false positive, but I would like to be sure like you.
Did you find more information regarding this MCE ?, did you solve it?
My hardware is:
gigabyte z590 master
cpu i7 10700k
ram 32 GB HyperX Fury Black dd34.