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
If you want the full fancy GitHub, they have an on-prem enterprise edition for $21/user/month. https://github.com/pricing
But if you don’t need all their bells and whistles, or the team doesn’t care about not having the GitHub interface, then the other suggestions are better.