1. It looks like you can append the following ESXi boot option which will allow you to bypass the unsupported CPU during the installation/upgrade. To do so, just use SHIFT+O (see VMware documentation for more details) and append the following:
allowLegacyCPU=True
2. Workaround ESXi CPU Unsupported Error
https://polarclouds.co.uk/workaround-esxi-cpu-unsupported-pt3/