A right-click context menu for Nautilus to convert images to PNG via ImageMagick.
If you don't want to use this extension, you can simply use ImageMagick terminal commands:
$ # Convert a single file:
$ magick my_file.webp my_file.png
$ # Or if you want to do lots of files at once:
$ magick mogrify -format PNG *.webp
$ meson setup build .
$ meson compile -C build
$
$ # Install to system's nautilus extensions dir:
$ meson install -C build