If you know of a community and you can’t find it in all, paste the whole URL in the search field ( https://lemmy.ml/c/linux ) and then you can subscribe.
This indicates your insurance there’s someone interested in this community and it’ll start getting future content
Only the first user would need to do this, for those after, the community will show when searching in all
There are currently a few communities about football (soccer)
Try to search in the community section using “All instances”
If you can’t find them, comment below and I’ll gather links to the ones I can see