I installed PhotonOS in a VM on VMware Fusion. The only things I changed where: allow root login trough SSH and I installed docker-compose
To play around I pulled a Nextcloud image and started the container. It couldn't start successfully because port 80 is in use from httpd on PhotonOS itself.
After I stopped httpd on PhotonOS the container could be started.
Is there any reason why httpd on PhotonOS should be started...?
Did you choose full deployment during the installation of Photon OS?
If yes, this is why you have httpd running. This is not the case if you choose minimal deployment during the installation.