Which kernel do you use on Debian? IIRC support for Intel Arc was added in 6.0 or higher. I am using Proxmox (based on Debian) and I had to upgrade from 5.15 to 6.2 kernel to get hardware decoding to work. Have you checked the Jellyfin manual? It’s pretty elaborate on how to get Intel QSV working.
What’s the alternative of
sudo make install
andcurl | sudo bash
if a package is not available in AUR? I am unfamiliar withmake install
.