I have set up a Fedora 39 desktop VM (and a Debian, Arch, Win11 one for testing as well) and it seems the German Alt-Gr + Q combination is not supported via Unraids VNC, no matter what I try or what distro I use.
This topic came up in various forums (Unraid, Proxmox, name it) and I tried (almost?) all the advices: removing SPICE, setting locale in the VM, (or VM creation UI or XML directly), remap Alt-Gr in Gnome/KDE, configuring keymaps, you name it....
I also tried Debian, Ubuntu and Arch and Windows 11. All installed VMs show the same behavior, so I think it's safe to assume it's a VNC issue.
Yet, many people also report they fixed it at some point (or they stopped bothering). So what's the secret sauce? I would like to use my VM mainly as personal, centralized email/browser client so having the @-character would be really convenient.
//edit: I installed xrdp on the Fedora VM to connect via RDP and all Alt-Gr characters work. So it's clearly a VNC issue.