Powershell Core on Photon OS does not built-in register PSGallery. Hence cmdlets install-module, find-module, etc. are not working.
Put some work on this. You may use one of the attached files.
As alternative, simply pull and run:
docker pull vmware/powerclicore:ubuntu16.04
docker run -it vmware/powerclicore:ubuntu16.04
tdnf install powershell installs powershell LTS version 7.0. Simply use install-module to install modules supported on Linux.
Sorry, Photon 2.0 does not include Pwsh7. Try this .photonos-scripts/Pwsh7.0.3OnPhotonOS.sh at master · dcasota/photonos-scripts · GitHub