Where to find comments component or chat features?

That’s not true. The back end tables work the same in Apps and Pages. Likewise, selecting data from those tables works the same. It’s very likely that the Relation thay your Lookup is referring to is a multiple relation. It needs to be a single relation.

  • A Lookup column that can retrieve values from multiple rows will become an array. Arrays can contain multiple values. Even if an array contains only one value, it is still an array and could potentially have multiple values in the future. Most importantly, you cannot place an array value with multiple values into a container that will only hold one single value.
  • A lookup column that retrieves values from ONLY one row will be a single value instead of an array. A single value can be placed in a container that holds a single value.