The SD card thing
Starting with vSphere 7.0, SD cards and USB boot devices are no longer supported. These devices cannot handle the new partitioning scheme. Unlike 6.x and previous versions, the boot device is now used for logs, which can cause issues when said devices aren't rated for frequent writes.
The solution is to use a write-intensive local boot disk, or boot from SAN.
VMware KB: https://kb.vmware.com/s/article/85685
vVol minimum size change
In vSphere 8.0 and below, the minimum size for Virtual Volumes is 4GB. Starting with 8.0 Update 1, the size has been updated to 255GB. Any vVols that existed prior to upgrade may disappear, or other errors may occur if you try to make a vVol smaller than 255GB.
The solution is to increase vVols to 255GB or larger, and create new vVols at the same or larger capacity. A workaround exists, which allows the smaller vVols to be used, by using the following command:
esxcli system settings advanced set -o /VVOL/vvolUseVMFS6AndLargeConfigVVols -i 0
VMware KB: https://kb.vmware.com/s/article/90791
An unpleasant surprise awaited me in upgrading to vSphere 8.0 Update 2. The workhorse servers in my homelab are all first generation Xeon Scalable (Skylake), and have been put on notice that they may not be supported in future releases of vSphere. Granted, the processors are 5 years old, but Naples-based AMD EPYC are 6 years and do not have this warning, and Broadwell processors (E5-26xx v4) are still supported as well.
The solution is to append a boot option when loading ESXi, although this is a band-aid that probably shouldn't be used in production as it may cause instability. Using SHIFT+O prior to module load, use the following: allowLegacyCPU=true
VMware KB: https://kb.vmware.com/s/article/82794