Could I make a game with Photon then publish it to Steam like I would usually?

Before you publish your game to anywhere, you should make sure you have authentication setup, in your case if you plan to publish on Steam, you will want to log into your account on the Photon website, manage your app for your game, and scroll down, you should find Steam Authentication along with many others - this ensures that someone who plays your game actually owns a legit copy of your game, and that your app ID is being used for your game specifically - there are a few steps involved for setting up authentication correctly and testing it before publishing, here are the docs for authentication: https://doc.photonengine.com/en-us/pun/v1/connection-and-authentication/authentication/custom-authentication

There are also notes for Steam: https://doc.photonengine.com/en-us/realtime/current/connection-and-authentication/authentication/steam-auth - however, there are other API's like FacePunch: https://wiki.facepunch.com/steamworks/ who also have authentication methods as an alternative