When starting Picard without pygit2 being available the plugin options page shows an error message. This behaves differently from starting Picard with "--no-plugins".
Ideally starting Picard with "--no-plugins" to intentionally disable plugins or running and without pygit2 and this having plugins technically not available should result in similar behavior and cleanly disable the plugin functionality.
Generally it might be better to not show the plugin options at all in both cases, as existing functionality there might result in further errors.