I have 2 posts types. One called Tours and the other called Places To Stay.
I've added relationships between them and when I try to add Places to Stay to a Tour template, I can't see the relevant fields.
Please see the following video screenshot for more details: hidden link
In this case you will need to have a view that is displaying the intermediary CPT in order to display the relationship fields as you won't be able to access them like this.
I followed your CPT relationship guide and am not sure why I need intermediary CPT but as long as it will work I'm ok with it.
Please explain what exactly you mean that I have to do.
I really don't want to start working with shortcodes.
I did some more testing on this one and found that you can do it with the Single field block. From your video you are using the Image block which I believe doesn't seem to allow for the data to be pulled.
In my testing you are able to select the intermediary fields. As a workaround you can use the single field block to display the image.
I've tried this but even when using a single field I only see the current post type (Tours) fields and not the related post type (Places to stay).
You can see it in the video: hidden link
I saw the issue why your relationship wasn't showing up. The content template was previewing a post that did have a places to stay relationship established.
If you switch the preview to The Cube Houses, Rotterdam you will now see your relationship showing up for the dynamic sources.