Desktop and mobile versions within one url

[Arhel]

Colleagues, tell me how to do it right. There is a site that uses 2 templates at the same time: desktop and mobile (just a mobile template, not adaptive!), The version given to the visitor is determined based on the user agent. Accordingly, the mobile version is slightly simplified and does not display some of the content to the user from the phone.

The question is, how will such a project be doing with indexing? Which version of the template will the search engine robot see and which will it ignore? Do I need to somehow additionally show the robot that this is for a desktop, and this is for a mobile?

Thank you for the detailed answers.

 

[Artem]

If the urls of the mobile version of the site are different, then these are unique pages and they will be indexed separately

 

[Jonndein]

If the urls of the mobile version of the site are different, then these are unique pages and they will be indexed separately

I disagree, search engines are gluing pages of the mobile and desktop versions of the site