If the menu is available on a website you can link to it by adding the website:menu tag. These will show on Organic Maps for example

https://wiki.openstreetmap.org/wiki/Key%3Awebsite%3Amenu

See for example this bar that Organic Maps shows the link to the Menu:

Mate Bar https://omaps.app/0ysrTcXR-t/Mate_Bar om://0ysrTcXR-t/Mate_Bar

I've also wondered this. I'd also like to contribute info on how busy places generally are around me, so you know to show up early if you want a table, or don't bother dining in on a weekend, etc.

Apparently MapComplete integrated mangrove.reviews, and you can upload pictures from MapComplete, so that may be the best option for now?

There's also https://lib.reviews/ which is Creative Commons licensed. Looks like there's open issues to integrate that into OSM via a plugin: https://github.com/eloquence/lib.reviews/issues/319

For photos, Wikimedia Commons seems like the best approach, although really any website will do (as long as there are no licensing issues w/ that site and OSM). There is a whole wiki page about linking OSM features to photos.

Unsure about reviews, though.

Not specifically for restaurant menus, but more generally if you’d like to contribute to Open Street Map while out and about, depending on your area there may not be complete information for a lot of businesses. You can use an app like Go Map!! on iOS or Street Complete on Android (or many other OSM apps) to add information like business hours, website, phone number, and other useful information.

@ApplyingAutomation You can use https://mapcomplete.org/food for this - it has reviews (thanks to @mangroveReviews ) and picture upload

Wikipedia page maybe?