Where the binaries were build, it was with glibc 2.34, which is too recent for the freedesktop-sdk. They are also likely to fail on any other distro that people use, so it’s not an exception.
Ideally you’d build everything inside with flatpak (don’t ask me how I don’t know Flutter) instead of repacking random binaries.
Thank you! That’s strange because I built the app, the flatpak and installed the app all with the same PC. Anyway, I managed to build the app within a containerized environment and now it works! Thank you!