In case when remote control capabilities are not required, one could use jitsi (https://jitsi.org) video conferencing service which provides screen sharing capabilities (implementation depends on the web browser).

The main advantage is that there is no need to install any software neither on the remote machine nor on the local one.

There is a cloud hosted free version https://meet.jit.si which does not even require registration.

For those of you who need to try it out real quick : Jitsi Docker : https://github.com/jitsi/docker-jitsi-meet

I haven't tried this, but I imagine a situation where computer A uses SSH to connect to VPS B and computer C connect to VPS B using SSH. If both SSH connections port-forward a VNC port, you can use VNC.

Yes technically it could work, but I cannot ask the users to use SSH and configure VNC. The force of team viewer is that you download it, open it, and give number over the phone and it works.

Chrome remote desktop works pretty well

But for remote control, it stops after every few minutes, asking the "controlled" user to click on a button to continue. Not so practical in a few situations.

What do you mean? I've never had it do that.

It always happens for me when accessing a Linux machine remotely. I can't find a screenshot now, so the next time I do it, I'll take one. It seems to be a security measure, to prevent someone from sharing remote access and then forgetting about it afterwards, but it makes for terrible usability.

This is what I use. In Unix it just works (TM). If you have an ssh client in windows, it also works with Remote Desktop via ssh port forwarding. In lieu of a (configured) ssh client on Windows, you can send the other person a self-contained Go program to do the job.

you can also port forward from/to unix sockets

Not OSS but remotedesktop.google.com works well.

It sucks for multi monitor setups though, keyboard events, defocuses for no reason, unlocks the computer you rdp into, doesn't support scaling monitors.

I don't know how smooth it is, since I haven't tried it myself yet, but apparently Nextcloud talk can do it. I think it needs a browser extension but that might not be nearly as much of an imposition as vnc + ssh. It's also pretty easy to self host on a vps or other server of your own.

I use nomachine behind vpn and it works much smoother than teamviewer. It's multiplatform and free for personal use.

In the same boat, and I have heard good things about https://www.dwservice.net/fr/home.html, but I haven't tried it myself yet.

zerotier.com is exactly this. I am still amazed how easy this is. (Big fanboy)

Not opensource but works good: https://www.cloudberrylab.com/remote-assistant.aspx

Anybody know of a UDP-based alternative? VNC is TCP.

Is there a reason why you need UDP specifically?

It's far smoother.

What protocol do you notice this with? In my experience, Microsoft RDP (the only protocol I know with configurable udp and tcp) with and without udp is imperceptible during typical use (eg. server administration).

With RDP. It's not imperceptible for me. I don't just use RDP for server administration.

I've been looking at a combination of SoftEther (for dynamic IPs) and Guacamole to replace TeamViewer, ConnectWise, etc.

I also use Guacamole for remote employee/vendor access (with public IPs hidden behind a proxy like an F5 or at least SSL+HTTP Simple Auth), but I haven't ever tried to configure it for remote support session sharing type stuff. Is that how you're using it? If so, how is it set up?