> What kind of firmware updates do you need to do on it, when its only purpose is to act as a screen?

On some screens, signal processing has been significantly improved in later firmware versions. New features are also not uncommon, such as VRR and HFR being added after release[1]. This is particularity nice for modern consoles.

[1] https://www.flatpanelshd.com/news.php?subaction=showfull&id=...