I know folks are going to recommend RawTherapee and Darktable, and those are some admirable projects, but I also know that a lot of long-time Lightroom users bounce off of them. I'd still encourage you to give them a try, but also if you're willing to catalog what things are missing and provide feedback to those teams. Even better if you're willing and able to help make the change you want to see in OSS, but additional reinforcement on the things that are misses currently in their offerings will help strengthen those projects.