I encountered this today for the first time. I've used a Family 365 subscription for a number of years.
The problem was present only intermittently, and in the Edge, Brave, and Chrome browsers. I had been refreshing the screen in Edge from time to time this afternoon, and eventually the screen displayed correctly, in Edge. I then confirmed it was correctly displaying in Brave and Chrome.
I was able to view the contents of my OneDrive, throughout the entire episode, using the Android OneDrive application.
I suspect there's a problem at Microsoft's end, since at no time did I make a change in browser settings or anything else on my WIndows 11 Pro laptop, between the time I began to experience the problem and the screen eventually rendered correctly. I also see there are others here reporting they tried different browsers - and sometimes different PCs - with the same problem occurring. This also suggests to me the problem is on Microsoft's end.
I would be interested in hearing if the problem is only being experienced by Family 365 subscribers or if this is a problem being seen by Business 365 subscribers, too.