Hello! I have the same problem.
Affected packages : warehouse, flatseal, authentificator
Broken apps just show white blank window.
Strange thing that it's running on the same runtime as Dbeaver - but Dbeaver works as usual.
What i have already done:
1) flatpak repair
2) flatpak uninstall --delete-data org.freedesktop.Sdk org.freedesktop.Platform
then flatpak repair then reinstalling SDK+Platform
3) flatpak uninstall --unused
4)And radical way
flatpak uninstall --all --delete-data -y
sudo rm -rf /var/lib/flatpak
sudo apt remove --purge flatpak
sudo apt --fix-broken install
Restarted the PC
Then did full reinstall of flatpak + adding flathub + installing apps- ZERO EFFECT
System: Debian 12
Kernel: 6.1.0-37-amd64
DE: Plasma 5.27.5 (Wayland)
GPU: Intel HD Graphics
All apps broke after installing the latest updates for flatpak via Discover yesterday