Edit: this is not gimp related at all but probably just the issue of my screen calibration. I'll pluck away at it until its right, thanks for all the help.
Edit 2: installing an ICC profile has made a significant difference and the mushroom are a bit over saturated but not exactly glowing anymore.
I know both of these photos are oversaturated, I am working on a laptop with a pretty shit screen so all of my photos look awful. I am trying to fix it but I'd like to fix this first.
Gimp 3.0.4 This is the exact same file, the left is displayed on gimp and the right is the saved .jpg in the linux mint photo viewer. The right side photo is so much more saturated than the left. The mushrooms look like they're glowing. Boxes ticked on save: progressive (in options), optimized (advance options) save colour profile (in metadata) - I have saved without colour profile and same effect.
This seems to be an issue with GIMP but I don't use any other editing software on my laptop so who knows. When I post these photos online the effect is the same as on the right. When viewing online, sometimes the photo will be normal but when you click through to the full image it loads as oversaturated. I'm sure there is something so simple I am overlooking but I just can't think of what.
Please let me know if you need more info!
This is the original photo, no editing open in gimp and photo viewer:
I've opened the edited photo and the original in krita and I could see the same effect when viewing saved jpg, so not exclusive to gimp. I've installed a different image viewer and it does seem to be the stock image viewer adding saturation. I am a bit confused as to why the same effect would happen when uploading these online.