Stuttering Videos

While Fedora39, under wayland with Niri, the laptop screen does not have issues with Youtube videos played in Firefox, the external monitor (Dell S2721QS) whether connected via the HDMI expansion port, or a USB hub connected in USB-C, has videos sputtering (freezing and then restarting few frames skipped). Interestingly, the sound never gets any interruption and plays flawlessly.

I received a USB-C to Digital and I have no issue with the videos when plugged from the GPU USB-C output, with exactly the same settings on the computer.
So it seems it’s an issue with the extension cards. I have the USB-C to the back (where power is higher) and the HDMI expansion on the left when facing the screen just before the USB-C (so 2nd slot).

What could I do to avoid that?

I dont think there is anything you can do right now to avoid that frame skipping. From experiencing kinda the same issue as you with my desktop 7900xt, it most likely yet another driver bug. All you or I can do is wait for a driver update. It sucks, but just like the vr support on the framework not working, the GPU has a very buggy driver right now.

The cards looks to route through the iGPU not the dedicated. One thing to try to verify the HDMI card is working, as I saw a reviewer do this, is remove it and plug it into the dedicated USB C port on the back of the dedicated GPU and see if you have a video issue. If not the card at least works.