My company has used Phabricator, which is an alternative to Azure Devops, for about 5 years. A few days ago they announced that the project won't be maintained anymore, so we are looking into alternatives. We have around 50 devs+product folks that use Phabricator at the moment. Source: about 3 years ago

You also mention Gitlab is close to what you would like - maybe Phabricator is even closer: https://phacility.com/phabricator/. Source: about 3 years ago

Https://phacility.com/phabricator/ I think checks most of those boxes, maybe all. Source: about 3 years ago

Visual Studio Live Share is an extension for the popular Visual Studio Code IDE that allows developers to bring their peers into their editor. You can send an invite link to let your colleagues write, edit, and debug code as if they were in the same physical location as you. This removes the challenges of working remotely when it comes to pair programming and brainstorming together. - Source: dev.to / 8 months ago

Have you checked out Live Share? It's included in VS and there's an extension for VS Code. Source: about 1 year ago

Visual Studio has collaboration tools. Source: about 1 year ago

Pair programming is when two developers work together at one workstation. Not necessarily on the same computer, but they work together on the same programming task. In remote work I love to use Visual Studio Live Share ❤️. - Source: dev.to / over 1 year ago

But there's also an extension that MS put out called Live Share. They have a version for both VS and VS Code. I've used the VSC one myself, to great effect. Source: over 1 year ago