We recently ran an ESXi upgrade from v6.7 to 7.0 and upon first boot received an ominous "No compatible network adapter found" error message. Turns out our server is using an Intel Corporation 82575EB Gigabit Network Connection NIC which is now unsupported. Ug.

A bunch of Googling gave hope that a driver could be manually installed so we followed the steps below, but to no avail. It looks like a "Shift-R" downgrade will be necessary. However, these steps to install the Community Networking Driver may help someone else in the same boat!

Download Fling networking driver here: https://flings.vmware.com/community-networking-driver-for-esxi
Rename the file net-com.zip and copy to USB stick

Log into VMware CLI from console <Alt-F1> and stop USB arbitrator:
/etc/init.d/usbarbitrator stop

List USB devices - determine which mpx.vmhba# is the one you just plugged in:
vbq -q

Copy file from USB stick (using mpx.vmhba# + :1 for partition 1):
mcopy -i "/dev/disks/mpx.vmhba36:C0:T0:L0:1" ::net-com.zip /tmp/net-com.zip

Install module:
esxcli software vib install -d /tmp/net-com.zip

Show NIC cards:
esxcfg-nics -l

We can also try enabling the ne1000 network module:
esxcli system module set -e true -m ne1000


Good luck!