Stackoverflow Question - Select where id in variable does not work

gistfile1.txt

CREATE TABLE Users (ID int, Username varchar(100), isActive TINYINT);
CREATE TABLE UserActions (ID int, User_ID int, Type varchar(100), ActionDate Date);

INSERT INTO 
	Users(ID, Username, isActive)
VALUES
	(1, 'Ben Busy',1),
    (2, 'Lui Lazy',1),
    (3, 'Emmy Eager',1),
    (4, 'Lana Later',1);
    
INSERT INTO 
	UserActions(ID, User_ID, Type, ActionDate)
VALUES
	(1, 1, 'Login', '2021-01-01'),
    (2, 3, 'Login', '2021-01-02'),
    (3, 1, 'Login', '2021-01-02'),
    (4, 1, 'Login', '2021-01-03');

SELECT u.ID, u.Username, ua.ActionDate FROM Users u LEFT JOIN UserActions ua
       ON u.ID = ua.User_ID
       AND (ua.Type = "Login" OR ua.Type = NULL);
              
SET @userIDs := (
    SELECT GROUP_CONCAT(u.ID SEPARATOR ', ') FROM Users u LEFT JOIN UserActions ua
              ON u.ID = ua.User_ID
              AND (ua.Type = "Login" OR ua.Type = NULL)
    WHERE ua.ActionDate IS NULL);

SELECT @userIDs;

SELECT * FROM Users WHERE ID in (@userIDs); -- only retunrs Lui Lazy but not Lana Later

See sqlfiddle under http://sqlfiddle.com/#!9/3563eef/8

This is my attempt to avoid a temp table

         UPDATE Users INNER JOIN 
         (
             SELECT u.ID FROM Users u LEFT JOIN UserActions ua           
                         ON u.ID = ua.User_ID   AND (ua.Type = "Login" OR ua.Type = NULL)  
                         WHERE ua.ActionDate IS NULL
         ) as subquery     
           ON u.ID = subquery.ID  set u.ID = 0;  

but it was not running on fiddle (time out)