Currently with the Steam Play Proton Linux compatibility layer, Red Dead Redemption 2 isn't playable but a new testing build provided by a CodeWeavers developer sounds promising.
With the official builds of Proton, it just doesn't work and people have been tinkering away on different ideas to get it working for about half a year now. That looks like it's about to change. A CodeWeavers developer, Brendan Shanks, made a post on GitHub containing a new build for people to try that should hopefully allow you to play Red Dead Redemption 2 on desktop Linux.
It does require some manual effort to get running like having the latest NVIDIA Vulkan Beta driver "to avoid very poor performance" or for AMD having a patch applied by building it yourself "otherwise it will crash halfway through the progress bar". There's also a few issues with it, like only having 720p and 1080p resolutions working. Progress is progress though right? Eventually the issues will reduce and in a few more months it might even be easily playable.
Steam Play and Proton definitely open up a lot of doors for a Linux gamer. Don't know what it is? Check out our little dedicated page.
As a sidenote: if you do have access to Stadia and good enough internet, Red Dead Redemption 2 can also be played there since Stadia works on Linux.