Some GTK flatpak apps look really strange on Fedora Silverblue. This is the case on several PCs in our home, and it’s been like this for over a year now.
The examples above are from the “Secrets” app, but this happens in many other apps too. I am not using a custom theme, just the “Adwaita-dark” flatpak version.
I installed gnome-tweaks with rpm-ostree and set the legacy theme, but it changed nothing. Apparently the problem is with newer apps using libadwaita, not older ones.