Downloaded the class 20 as a singular DLC and the loco has not shown up , I would also like to point out that it doesn’t say it needed the Darlington route in order to be shown in my collection , any help with this would be greatly appreciated!
Not sure where it told you Tees Valley wasn’t required becuse I’m 90% sure it is. A lot of the older loco addons were never decoupled from their routes
Wasn't it anything released after TSW3 or something like that and anything before was still bespoked. Its been awhile since this question came up last but I think that was the answer.
Anything released before TSW3 and Training Centre still needs the base route to show up under loco selection. For the class 31 and class 20, Tees Valley is required, even in the newer versions of TSW.