We are changing our system. We settled on git (but are open for alternatives) as long as we can selfhost it on our own machines.
Specs
Must have
- hosted on promise
 - reliabile
 - unlikely to be discontinued in the next >5 years
 - for a group of at least 20 people
 
Plus
- gui / windows integration
 


Gitea or forgejo, for hosting your repo and managing access rights. WoodpeckerCI when you eventually need a CI/CD. (Is a fork of DroneCI and integrates nicely with gitea.)