I want to setup PA desktop flow on window server 2019/ window 10 running on a private network that do not have access to internet.
Is there a possible way to do it ?

I want to setup PA desktop flow on window server 2019/ window 10 running on a private network that do not have access to internet.
Is there a possible way to do it ?
Not possibile. You can limit your data to be processed onprem but you cannot run without connectivity to the MS services.
These are used for storing flwo definitions, access controll to environments and flows, logs etc.
You can drop any traffic except connectivty to MS as per below:
https://learn.microsoft.com/en-us/power-automate/ip-address-configuration