And MS has another old issue raising its head again, mostly due to inattention during the "last minute release week furor" I suspect.
As we barrel down into release week, Win 10 is currently preset to not allow the user access to the boot loader, which means you can't easily go add a Linux as a dual boot. Your existing Linux should remain OK since you are update/upgrading, but adding a new Linux down the road might be problematical.
This means a little something here in America, but in Europe it is a real deal killer if it is permitted to remain that way through the end of this week.
This is all part and parcel of the forced upgrade mess currently going on, Win 10 is obviously intended to be run from MS's end
and the users become just users of a no-charge system that is totally controlled by MS. MS is shutting down that which conflicts with that forced upgrade system.
This will actually not fly very well with the hard core Windows boys who want to tweek their Windows systems to suit themselves --- and it will get EU action called down on MS head right shortly if it remains set that way, even on the free Win 10 version.
EU actions on false advertising are already being primed, for whenever Win 10 rolls over to the subscription model and isn't "free" as originally advertised. MS has already bit that bullet by their advertising so if they charge for Win 10, ever, they get that EU legal action right up the nose.
It is suspected that the future subscription paid versions will have these sorts of uglies removed, but if you just want to stick with the free Win 10 you get what you get.
Sorta like all those other free Windows world trial softwares that wind up being crippled in some critical fashion to encourage you to shell out for the premium version later on.
Me, I see Free Win 10 being a transition version, intended mainly to kill off all past legal requirements for all old versions -- with Win 10 to be replaced by Win 11 as soon as all the legal dust settles with Win 11 being structured as pay me from the get go.
BTW, since you are legally transferring your old license over to the new Win 10 license, your old software license ENDS totally and you have a case of "you can't go back" looking you in the eye if you decide you don't really like Win 10.
This will get challenged and reversed in the EU eventually as well.
But you don't live in the EU, now do you?