I just upgraded our fleet of gateways to 8.1.28 using EAM remote upgrade, as I usually do.
Each gateway required a visit to the homepage to acknowledge the terms and conditions on the commissioning page before the gateway would start. EAM did say that, though.
This was not the case in the recent past and it adds additional friction to upgrading these gateways.
Is there a global acknowledge so one can skip this commissioning step when upgrading via EAM?
Yes, you can set an environment variable in your gateways to accept the EULA. You'd have to do that everywhere (in a SystemD override file is typical) before the upgrades. I don't imagine there's any harm in leaving it there all the time.
Is there a way to achieve this with Windows and EAM gateways?
No idea. Probably? But I'm not a masochist. Others may chime in.
Almost certainly not just with EAM. This particular function has to be present in the remote gateway before it starts.
It looks like it might be off to Registry Editor to set environment variables for Windows services (I'm unsure if there is a UI for this hidden somewhere 
):
Looks like you can go to HKLM\SYSTEM\CurrentControlSet\Services\<service name> and define a Multi-String registry key called Environment and put individual <name>=<value> definitions on each line. The key wasn't there for me after a fresh installation. Upon submitting, it produced a warning about stripping empty strings (even though I tried to not have a blank newline in the value data) but seemed to work just fine.
With Windows you could probably even distribute this via Group Policy if your machines are domain-joined.
That fits my prior comment.
