This is one thing I'm surprised the open source community hasn't developed a popular alternative for: Teamviewer.

The core idea is simple: a video stream from one computer to another, with mouse and keyboard controls sent the other way. Connection negotiation can be done Magic Wormhole style, via basic STUN, encryption can be done in a number of ways. Add some clipboard and P2P file transfer features and you've got most of Teamviewer/Anydesk/whatever implemented. There's VNC, but that's horribly outdated and the UX is absolutely terrible.

I think there's a business to be built here; open source remote support with a Gitlab-style self-hosted option companies can put down in their own networks, or have them pay you for management and servers.

This project is a good starting place, as any. With some tweaks you could probably build this into a end-user friendly system with your usual numeric code and random password. There's a business to be built in this space, I'm sure of it. I wish I had the expertise to take advantage of that.