Is there a debuginfod?

i want to see a stack trace but org.gnome.Sdk.Debug is “< 5,7 GB” which i would prefer not to download.

in some distros you can use DEBUGINFOD_URLS="" gdb and it will download needed debug files on the fly

is there such a server for flathub?

no, there is not. If I remember there is a PR for flatpak that would allow generating the proper data, but it’s still open.