To repeat myself and other Canadians here NO THEY CAN'T. They aren't Canadian citizens and can't become Canadian citizens. Canadian citizenship is a process that takes years to acquire and neither of them qualify. You can't become a citizen just because you want to - all countries set up laws and rules that have to be followed. In Canada NO ONE is exempt from following our laws and rules, "the problem" is suggesting that someone is entitled to flout our laws or get an exception because of who they are.
There are many, many deserving people who want to come here and can't. Many of them can support themselves and pay taxes. If the Canadian government no longer allows investor/business class immigrants (very wealthy people who want to start companies here and employ many Canadians) why would we allow a British prince to bypass the rules? We are a separate independent country from the UK with our own laws and rules. The days of us being a mere colony are long over. They are welcome to visit here but they have no more entitlement to live here than other people. Just because Harry is royalty doesn't mean they they have the right to circumvent the rules that all our other immigrants have followed.
If Harry is given some special diplomatic role by the British government, it is possible that terms can be negotiated for him to remain although he doesn't strike me as qualified in that area.
For someone who lives in Denmark ,you hold very strong opinions about our government and aren't listening to the Canadians here who said it won't fly here.
Our current federal government is a minority one and holding onto power with a very narrow margin (they were nearly defeated in the last election). In our system, the government can fall at any time especially when they have a narrow minority. All it takes is the opposition passing a non confidence motion which passes (the opposition parties currently outnumber the ruling party), the government falls and an election is triggered and defeat usually results. Often the new government undoes the action that caused the defeat of the previous government. (This has happened in the past a number of times.) Prime Minister Trudeau and the Liberals will avoid antagonizing the voters (the majority who are taxpayers) with an unpopular decision that could lead to a fast defeat.
I repeat they are welcome to visit here but they don't get to bypass our laws and rules and we don't want to pay for their security because they are not coming as a royal tour but privately. Canada only provides this type of personal security for visiting heads of state and royals on official tours. When Harry's been here before privately or doing charity work like the Invictus Games, our government has NOT paid for it. Visiting celebrities pay for private security THEMSELVES. BTW Canadian citizens ARE NOT entitled to taxpayer paid individual protection. You seem to be confusing regular police services for which all residents and visitors are entitled to (citizenship doesn't matter for that at all) with personal security and bodyguards which what we are talking about. If a Canadian needs bodyguards or personal security, THEY pay for it or someone else on their behalf (like a company or organization) pays for it, NOT our government. That is NOT a service provided for by our police to ANYONE here including Canadian citizens (which they are NOT and CANNOT become. The exception is our Prime Minister who is our HEAD OF STATE and therefore receives government paid personal security (BTW, it isn't the local police that provide it, it's the national police, RCMP). Prince Harry is NOT our head of state. Other people who need personal security here pay for it themselves. Yes Harry and Meghan will need security but we will NOT pay for it.