Weird fade into darkness when using Linear colour space

I've recently changed my default render pipeline project to use linear colour space as I heard it could produce better looking scenes, however I've come across this issue where when light meets the darker areas of the scene, it creates this ugly-looking gradient. It feels like rather than a smooth transition from light to dark, it instead has 4 distinct rings of colour.

(note: the effect is much stronger in-game, the screenshot does not do it justice)

Any suggestions as to how to fix/change this would be greatly appreciated. The second image I provided is an example of a scene in linear colour space that has a smooth fade from light to dark, which is what I want to achieve.