Kind of late to the party but i just want to add that I used reaper on wine just 3 months before its official Linux release and after that i just started using it natively. I currently use LinVst (
https://github.com/osxmidi/LinVst) for all my vsts and I have 0 complaints other than ofcourse vst support but that's a different issue, there are native linux plugins which are also good and get the job done. As far as "viable" I would say that it is very viable. Think about it like this; there are alot of linux distros and alot of people that use it for different needs. Right now besides ardour Reaper is software that even rivals protools and is on Linux, windows has alot of bloat and its upgrade process is just terrible (wiping drives, things getting possibly corrupted, lots of forced updates, etc) with Linux you dont even have to migrate everytime there is a big distro upgrade, hell you can even choose not to upgrade, all of that is something that production studios can benefit from and if reaper keeps its linux support on point then is only a matter of time before adoption as the userbase keeps growing.