@bignotlive Thanks for the screenshots and other info.
Your CPU-Z is really old (from 2017) and isn’t recognising the CPU correctly - if you download the latest version it should hopefully correct the name.
As shown in the pictures there are no errors in device manager and drivers are up to date so we can rule them out.
You have tried different microcode and even Linux OS (which was a great idea) and the problem persists, so at this point I am leaning towards possible hardware failure (AMD GPU and/or RAM) that might have coincided with the BIOS update.
Do you know what the BIOS version was prior to it being updated?
I’ll have a search around and see if I can find a complete BIOS dump from another Nuc8i7hvk that may be an earlier version, although we would need to replace the MAC (at the least) and possibly the UUID and serial number (if present).
[Edit] Another possibility is that the VBIOS of the Radeon RX Vega M GH is corrupt.
[Edit2] I could only find a complete dump on Vinafix from 2019 but it doesn’t say which version it is (it also includes the EC EEPROM dumps).
You may be able to use the ‘F7’ method to flash back to an older version such as 0059 from Intel’s forums. (not a dump but it is the original 9MB .bio file)
Link to BIOS Update and Recovery Instructions for Intel® NUC (see F7 update).