I've looked everywhere and the answers have been pretty mixed from absolutely not, to yes, some even said only sapphire cards had the switch. They were generally older forums posts so I was wondering now if there was a definite answer now
The one I got certainly does (Powercolor reference version) and there's no real reason for any others not to except to say that some card manufacturers "might" choose to only include UEFI or add a physical switch to select between them (Sapphire tend to do this).
Personally I don't like having to jump through hoops just to get your PC to boot (stuff like reformatting hard drives and so on) so given a choice I either go for legacy or disable secure booting (and I have no need for secured booting anyway). I've only ever seen one GPU that didn't support legacy booting and it was an R9 380 (can't recall manufacturer and I swapped it for an MSI R9 270x that did work anyway)