Another vote for GIMP, though I believe they still don't have full CMYK support yet. VIVA (?) I think has a Photoshop clone, but pretty sure not open source.
Yes but it does have some editing and metadata management features. Personal opinion is everyone should start with a photo manager and then only use another program if you need more. On Linux Shotwell is another photo manager and Digikam is cross platform. I know my wife uses just Shotwell. She has never needed more. I use Digikam because it is a little more powerful and flexible but less elegant. My wife is into photos... me not as much too.
How extensive of editing are we talking? If you just need some of the more basic features, there is Paint.NET which is surprisingly useful for a lot more than you'd think. Definitely not as feature-rich as Photoshop though.
I use Krita for infrequent no-stakes photo editing (and even pixel art at one point), might not be for everyone but there's a lot of overlap. Also you can use G'MIC with Krita, so that might help.
I think we both know there are better ways to communicate when trying to be helpful, namely ways that are not tinged with shaming/condescendion. I hope the rest of your weekend is nice as well.
Nothing I wrote was condescending or shamed the person for asking what they asked. Unfortunately, people like you live in technical forums all across the internet. You make a snap judgment that an on-topic focused response is an attack when it's not, and you decide to play the white knight. Meh.