Lightning record pages give you the freedom to customize the layout of your record pages. You can assign your record page to a specific Lightning app so that your users can see different layouts for records depending on the context.
How to deploy Lightning record page assignments
The record page itself has the Lightning page metadata type, and the Lightning app is a Custom application metadata type. First, include both of these types in your custom metadata filter and run a comparison.
The assignments are actually part of the Custom app 's XML. You can find them in the ProfileActionOverrides tags.
<profileActionOverrides>
<actionName>Tab</actionName>
<content>Sales_Home</content>
<formFactor>Large</formFactor>
<pageOrSobjectType>standard-home</pageOrSobjectType>
<type>Flexipage</type>
<profile>Custom: Sales Profile</profile>
</profileActionOverrides>
In the example above, I've assigned my record page Sales_Home to this app and the Custom: Sales Profile.
If you want to deploy the assignments, simply deploy the Custom App!