Just to clarify, it is true that they have a free version of up to 5 users but Perforce is not a service like GitHub or GitLab. Perforce only gives you the tool
You have to pay your own server (or have a computer in your closet running 24/7) to actually have a perforce server you can use.
If you want to self host your own perforce server, you can do it.
If you want to self host a Git server, I would recommend Gitea