My personal congratulations to the winners to complete the challenge in time
👍👏😎

different approach:

SELECT LI.id from FDRD_Com.List LI
JOIN FDRD_Com.Prod PR
ON LI.vehicle = PR.Car 
WHERE PE.ProductLineName='Toyota'
AND PR.Car is not null  -- might be obsolete

IN is expecting a list.

Did you ever try

select id from FDRD_Com.List where vehicle IN
(select LIST(Car) from FDRD_Com.Prod where ProductLineName='Toyota' and Car is not null)

on the sub select ?