I am a bit confused about the versions they say are safe. I'm running Bind 9.11 and their tester says there are no issues, and it supports all the necessary EDN

I am a bit confused about the versions they say are safe. I'm running Bind 9.11 and their tester says there are no issues, and it supports all the necessary EDNS behaviour. I think the point is that those versions mentioned will remove support for the bad behaviour, but it's not clear what you do need to do to prepare. I guess the only steps you can take are to run the tests and update to the latest version available.