I might be a little biased, but hear me out:
If he keeps the Canadian business setup its probably best to move residency to a jurisdiction which has a (non-shitty) DTT with Canada to avoid double tax residency.
I would︀ then choose the one with lowest withholding taxes and narrow it down to the jurisdiction︁ that applies the lowest total taxes on dividends.
https://taxsummaries.pwc.com/canada/corporate/withholding-taxes
Amongst those I would choose the︂ one which has great tax planning options, flexible to qualify as tax resident and easy︃ residence options. I also can't blame OP for his personal preferences.
Slovakia might be great︄ for passive income, but not so good for new business setup (21% CIT + 7%︅ WHT).
As Estonian resident he would pay 5% WHT on dividends only in Canada and︆ 0% in Estonia (in Cyprus/Malta 15%).
Estonia can also provide opportunities for future business setups︇ with much lower overall tax rate (e.g., 0%-5%).
A rather unique benefit of Estonia is︈ that it doesn't have in its laws management and control test for determining corporate tax︉ residence, so its less likely that Estonia would go after a foreign corporate structure.
Tax residency doesn't require any physical stay offering maximum flexibility.