Cover Variants and where to get them?

I recently got into buying and reading comics this past year and I’ve been enjoying my time reading some I’ve gotten.

With the new Magik solo run that’s happening, I’ve been very interested in getting some cover variants that I’ve been seeing. My question is: is there a site that keeps track of announced variants? Where are people usually seeing their news to preorder specific variants? And are there go to online sites that people use?

Thanks in advance!