Could you share the full URL you're hitting please? (and also, if you don't mind, which country you're in) We don't use PHP in the vast majority of our pages so this seems unusual and i'd like to debug more.

https://www.bbc.com/ (151.101.128.81) throws that error (here in Germany btw)

well, bbc.com redirects to www.bbc.com, page works in Firefox, fails in Chromium (raspbian Linux btw) with that fatal php error.

Isn't this more or less prefetch, as implemented by a number of browsers eg chrome? https://developers.google.com/chrome/whitepapers/prerender

I was looking for the same and came up with Moot - https://moot.it/

Looks like early days but it's pretty progressing tech-wise, well worth a look.

Not open source or self hosted? Can you point me to the repo link?