Just did what Claude said.
sudo apt install --reinstall bubblewrap
sudo tee /etc/apparmor.d/bwrap > /dev/null <<'EOF'
abi <abi/4.0>,
include <tunables/global>
profile bwrap /usr/bin/bwrap flags=(unconfined) {
userns,
include if exists <local/bwrap>
}
EOF
sudo apparmor_parser -r /etc/apparmor.d/bwrap
sudo aa-status | grep -i bwrapSummary of what was wrong and what fixed it:
- Ubuntu 24.04’s AppArmor hardening blocks unprivileged sandboxes (bwrap) by default, but the bubblewrap package ships no profile to exempt itself — so Nautilus’s sandboxed thumbnailer silently failed and cached that failure permanently.
- Adding /etc/apparmor.d/bwrap with a userns allow-rule (loaded via apparmor_parser -r) let bwrap work again.
- Clearing ~/.cache/thumbnails/fail and reopening the folder let Nautilus regenerate thumbnails successfully.