I tried DarkTable before, but I'm using RawTherapee now already for months, for processing RAW files to JPG.
And I'm using Gimp for editing.
All free open source software, works on Linux, Windows, Apple...
I'm using Linux btw, already for months now.
I tried RawTherapee long time ago. At that time it was not very usable, but I'm sure, they evolved, so it might be a good solution for many people. Problem often is, that many users, especially photographers don't know about open source alternatives of the Windows/MacOS-Adobe World.
But an even bigger problem is the lack in usability. I started using Linux before the Kernel hit the magic 1.0.x version with Slackware around 1992 and have it used ever since, wrote open source SW myself, much Unix stuff. My experience over all this time is, that there are very different definitions of "usability". The Unix/Linux-Nerd-Definition, which was (and still is in most regards) also my point of view, is that it is best to have extremely flexible and powerful building blocks of SW and competent users, who either are able to single handedly write their own kernel module to solve a problem (I did quite a few times...) or they are not worth to use that stuff anyway. In that world, usability means to be able to program and modify the tools and system to ones wishes.
The other extreme maybe is at least some parts of Windows/MacOS, where the user has no control over anything and just has to take, what is given to him.
Still, for most people, the computer is not even an interesting tool, but only just some tool, that is needed to get a result, but there is no love for it. This may be the biggest group of all users: not interested in the technology, but in the results with as little effort as possible and no need to think "logically" (like a programmer) what would be the most efficient way to do something, but just to do it intuitively. Successful products often have a good design and understanding of this desire. Linux, and almost all of its tools and programs have not... This is not evil-doing by the Linuxers, but a side effect of the culture behind Linux and open source. As I said, I'm not free of this behaviour myself.
So RawTherapee might be a good program, Gimp also in sense of being powerful as an image editor (at least since 16bit-editing finally arrives after years of promise...), but especially the workflow offered by Gimp is just horrible compared to modern engineered SW with a team of usability designers behind the hackers.
Yes, I can start and use Gimp on macOS, but it can be immediately seen, that its programmers never had a look into Apples design guides (or at least, they ignored them). A user that is used to the document-handling-patterns in Apples or Windows' ecosystem will just have a frustrating experience using Gimp as an image editor. Same was true for RawTherapee (I didn't try for some time now). It works on Unix/Linux and will behave somehow familiar for Linux-Users, but not for the other two.
I think, although I over-generalized pretty much here and being unfair towards some good efforts in the open source world, this is essentially an important reason, why Darktable, RawTherapee, Linux and so on are still not a real alternative and choice for many. Which is depressing, because if you just judge by feature lists, possibilities and price, one would wonder, why Adobe LR users still exist. But usability for the non-technical and plain user is the key. For that there is still no solution in open source.
(Sorry for the long post... This topic always makes me agitated)
