The NAPS2 Flatpak is compatible with officially-supported SANE scanners as well as network scanners using the ESCL driver.

Flatpaks use a sandbox for security purposes. Unfortunately, this prevents the NAPS2 Flatpak from using third-party SANE drivers to find other types of scanners.

If your scanner is listed with scanimage -L but doesn't show up in the NAPS2 Flatpak, you'll need to install NAPS2 from a DEB or RPM:

naps2-7.5.2-linux-x64.deb

naps2-7.5.2-linux-x64.rpm