Samsung Dex compatibility with DELL docks

I have a Samsung S10 phone with Samsung Dex. Dex is fun and can (sometimes) be quite useful. With it, I can use a desktop environment on my phone, like I would on a computer. My workplace is equipped with a wide range of Dell docking stations. For some reason, some get recognized by Dex. And some do not. For instance, Dex works immediately with the WD19 , but not with the TB16 or the WD15 . My questions: is there a (good) reason why not? How can I fix it?