Cooperative alternatives?

Sorry if this is treacherous heresy here. I know very little about WH40K.

I love seeing your minis and the collecting aspects. I wonder if there are cooperative alternatives or forms of these games, as my partner and I are not very competitive people. We enjoy expressing ourselves with our choice of... Idk, armies in the case of 40K, I guess. It'd be nice to find a system using minis that would allow cooperative gameplay, as I don't fancy collecting a buncha minis, and leaving them to sit. At the same time, I'm not creative enough to construct my own game system to meet these needs, so an existing structure would be nice. Thank you, Mini Masters. 🙇