Thanks to the Succession to the Throne Act of 2013, we know that in Canada, the rules for who inherits the crown can be changed by a simple majority in the House of Commons, ratified by the Senate, *without opening the constitution*
https://en.wikipedia.org/wiki/Succession_to_the_Throne_Act,_2013
The bill survived court challenges even
Soโhear me outโwith a simple bill passing in parliament, we could have the next queen of Canada chosen by random lottery among Canadians