It's not every day that we may welcome a new photographic raw file processor, but right at the start of 2020, there is one: ART! ART stands for Another RawTherapee, and indeed it is based on the latter. But the way you process your raw files in ART differs from its well-known 'mother'. One of the highlights of ART is the addition of local masking.
ART is made by the Italian programmer Alberto Griggio, who aimed to make RawTherapee easier to use while still keeping the well-known strengths of that program. At first sight the two programs look identical, but ART offers some new tools, deleted others or modified certain existing ones.The homepage for ART is at bitbucket/agriggio. There you can find a Windows version, an AppImage for Linux and a ppa for Linux (and the source code of course). A version for Mac OSX is on its way. On that same page you'll also find a link to the extensive RawPedia manual for RawTherapee. Many things written there apply 1-to-1 to ART, so that's a good starting point.
The following pages apply to ART v1.0 (edit: and later), released in January 2020 (edit: and later).