Yes, that’s it!
Had the same issue with this plugin (versions 2.3.0 and 2.3.1) and WP 5.6.
Please deactivate RLB, purge all your caches (if applicable) and reactivate the plugin.
All plugin settings will be preserved, the settings are accessible again and the “Gallery” entry should reappear in the admin (side) menu.
How to Get Support
After you register and login to the site, you may post all plugin support questions in the Support Forum.
If you need to provide private info, please create a ticket and then reply to it using Set as private reply option.