Related post plugins do not show up

Which related posts plugins are you using? You need one that is compatible with custom post types (like recipe in our case).

This one works, for example:
https://www.ads-software.com/plugins/yet-another-related-posts-plugin/

I tried with :

https://www.ads-software.com/plugins/related-posts-for-wp/

and

https://www.ads-software.com/plugins/wordpress-23-related-posts-plugin/

and neither of them work.

The first one only seems to support custom post types in its premium version. Not sure about the second one as I don’t see a reference to it.

I’ll have to recommend using one that does support custom post types (like the one I linked to). Take note that you usually have to explicitly enable it for recipes on their setting pages.

So WP Ultimate Recipe is not compatible with this 2 plugins which are top plugins (if not the best out there).

This means that WP Ultimate Recipe could not be compatible with lots of other plugins and this means that if we decide to use WP Ultimate Recipe we can reduce our options that are good and free. (plugins)

Anyways. Your plugin is very nice, and it has lots of good things, I like it, but because of this I can not use it. I don’t want to be constrained, I want to be free to use any plugin I want.

Those plugins are not compatible with custom post types which is the recommend way of creating custom content like recipes by WordPress. Unfortunately not all other plugins support them as well as normal posts, as you’ve seen, but there are plenty of other options out there.

Again, this one works fine: https://www.ads-software.com/plugins/yet-another-related-posts-plugin/

Using Custom Post Types allows us to do things that other recipe plugins don’t, so it’s up to you to decide, I guess.

You could have made a recipe plugin that will insert into posts and not to replace the posts. I don’t want to be dependent of a plugin because in case that plugin will not be maintained in the future or it will not be free anymore, I don’t want to loose everything or have a lot of work to transfer all the data to other system.

So I want to use posts not recipes. I want to insert the recipes into posts. This plugin offers that but in the same time keeps the recipes pages and that is a problem for duplicate content.

I’m afraid you’re about 2.5 years too late for that. We decided to go for custom post types as that’s the way WordPress recommends doing these things. There is no turning back now, really.