ok, that would rule out UBI for at least Europe.

I do not know how the Canadian constitution should comply with inequal payouts versus the right of equality, but in Germany, or for that sake any European country, citizenship-based UBI would not survive a case in the respective highest courts. It would not even get anywhere near there as some members of parliament know a bit about legal matters, too.
Or at least, they know, whom to ask.
Let alone the European court. Inequal treatment according to citizenship? No chance.
The mere idea would get fried in midair in a poltical debate.

Besides, the x years of waiting til citizenship would merely buffer and delay migration pressure. It would not solve the problem.

The only way to comply with the constitution would be to excempt foreigners from financing the UBI by means of tax allowances. Which would be tantamount to massive subsidies for foreign workers, hence disadvantages for citizens on the job market. Baaaad idea.

Creating a massive incentive for acquiring citizenship may not be a good idea either.