Further to what viper said:
A select list has only two parameters for each row - the value that will be returned, called "value" and the text that will be displayed, called "text"
So you need to build the string you want to display into a field called "text" something like this:
->select('CONCAT(firstname, " ", lastname) AS text');
so that the array only contains two items per row - "value" (which is the id field in your case) and "text"
$options = $db->loadObjectList();
// Merge any additional options in the XML definition.
$options = array_merge(parent::getOptions(), $options);
You could equally well get the data as you are and then build the string you want in php and create a new array with the correct text and return that.
Don't forget to merge in any options from the parent (eg a default value)
On Sat, 2021-04-24 at 02:22 -0700, Elvis wrote: