I switched to Unity 2020.3.18f1 and want to enable VR support which previously on Unity 2019 was (player>XR setting>VR support checkbox).
How can I enable VR support in 2020, I cannot find it ?
VR support has changed since 2020 as you’ve noticed. Everything has been moved to XR.
You can find here how to setup your project here in the manual
https://docs.unity3d.com/Manual/configuring-project-for-xr.html
Quite some things have changed over time. So be prepared to change some things (depending on how much you had implemented of course).
If you want a demo project there is the XR Interaction Toolkit example available on github
https://github.com/Unity-Technologies/XR-Interaction-Toolkit-Examples