Oh, my bad, I should have been clearer. I did also remove the function that deregisters jquery, so the bundled version of jquery was in place.
But again, once I noticed the CSS of the anchor tag, the jquery was irrelevant (for what I’ve tested so far*). I’m going to try tweaking the CSS.
There isn’t really any problem with the flex of the main-content, considering the whole website is rendered that way, but I do see how it can mess up the elements inside. I’ll call this a close for now, since my original problem was a blank page and now I know why, and if something else comes up I’ll come back.