Selecting from all databases from multiple tables
I would start by using information_schema.TABLES and COLUMNS to find which databases (table_schema) has what tables with the desired columns.

Then I would construct (via SELECT CONCAT("SELECT ", ...)...) the SELECT statements that contain references to all the tables/columns desired.

From them, copy and paste to run them.  Or put all of this in a Stored Procedure so that a single CALL can do all the work including executeing the constructed SELECTs.