Absolute fastest I can find on that site is a 747-400 at 752 knots / 866 mph but I do have a memory of one of that type breaking 800 knots over the Pacific within the last few years.
That site only includes submissions where the pilot took a photo of the instrument panel, so yeah, definitely not the true top speed record as I’m sure that not every pilot takes a photo, let alone knows of the site.
Anyway, still doesn't set an unofficial record by variant or type:
https://groundspeedrecords.com/wof-top-3/?aircraft-manufactu...
Absolute fastest I can find on that site is a 747-400 at 752 knots / 866 mph but I do have a memory of one of that type breaking 800 knots over the Pacific within the last few years.