[[migxLoopCollection?
&classname=`modUserProfile`
&tpl=`@CODE:[[+fullname]]==[[+internalKey]]`
&outputSeparator=`||`
&where=`{"primary_group":"2"}`
&joins=`[{"alias":"User","classname":"modUser","on":"User.id=modUserProfile.internalKey"}]`
]]
This question has been answered by Bruno17. See the first response.
[[migxLoopCollection?
&classname=`modUserProfile`
&tpl=`@CODE:[[+fullname]]==[[+internalKey]]`
&outputSeparator=`||`
&where=`{"User.primary_group":"2"}`
&joins=`[{"alias":"User"}]`
&debug=`0`
]]