Hello @cbsarge, welcome to the forum - and thanks for your interest in Duplicati!
As you may have noticed, the most stable version of Duplicati is still a beta version so, while it is very stable and many people use it without issue, it might not be the best choice right now for enterprise use.
That being said, your question about a “dedicated Duplicati server” leaves me a little confused. Duplicati only runs on the machine with content needing to be backed up - the destination for the files just has to be accessible by the Duplicati software (so local drive, network share, FTP, SFTP, cloud storage, etc.).
While the idea of a Duplicati server doesn’t really apply, on the machine where backups need to be run the question is a bit more applicable. Generally Duplicati doesn’t “need” a lot of resources to run - but running isn’t the same as running quickly.
At the moment, my guess is the biggest slow down is disk IO - particularly with the local database access, so having an SSD on which to store the local Duplicati database would be good.
The same goes for the temp folder usage - an SSD would be great, but having Duplicati do temp processing in memory (or on a ram drive) is good too.
If you’re wanting to use a high level of encryption then a fast CPU would be good.
On the Windows vs. Linux side, it shouldn’t really matter - but since Duplicati is written in .NET it will run “natively” on Windows but requires mono to run on Linux / MacOS. This isn’t a big deal, but it is an extra layer of software to have to maintain (mono isn’t the best at keeping SSL certificates up to date).
It really all depends on what your goal is - to run, to run fast, to saturate your bandwidth…it’s hard to say because it all depends so much on individual environments.