Aaaaaand the issue is fixed: your YouTube homepage should be back to a grid view – not the list view! Thanks for your patience while we worked to resolve this.https://twitter.com/TeamYouTube/status/1189934443856687104 …
Thanks for getting back to me. I had to disconnect my PC over an unrelated issue over the weekend. The graphics problem's gone now, but I have no idea why, or what caused it. If it comes back, I'll let you know whether clearing cache & cookies does anything.