Thank you everyone for the suggestions :), I think I've got what I need!
@rek Can you share what you chose? I'm using Affinity Photo a lot, it's good, but could be a lot better.
@nomand I just wanted to gather 'tried and tested' options for a friend. I sent them the two most-mentioned options in the replies: Darktable and Rawterapee (I had read about Darktable a little)
Gregory's Server
@rek Can you share what you chose? I'm using Affinity Photo a lot, it's good, but could be a lot better.