I still encounter this from time to time on clean installation of Aurora, so it may apply to Bazzite with KDE too. I believe this workaround is the cleanest way.
sudo mkdir /etc/systemd/system/sddm.service.d
sudo nano /etc/systemd/system/sddm.service.d/override.conf
And paste there this:
# Custom workaround for SDDM race condition
[Unit]
Wants=systemd-udev-settle.service
After=systemd-udev-settle.service