I can say that for Canada, yes, you're correct. It starts as of the day you left (or the day you become resident somewhere else, whichever is later) As long as you meet the requirements of non-residency. Which is basically no primary ties (spouse or dependants still living there, a house or car there). There are also secondary ties like bank accounts but these may or may not matter. You have to intend to leave permanently basically.

From a tax perspective you still are taxed on Canadian source income, so if your job is in Canada nothing changes.

With digital nomad visas specifically, as they are temporary and usually confer visitor status and not resident status, you may have difficulty establishing that you've left permanently and are resident elsewhere. That seems like a grey area yet to be tested, and the CRA probably has a good case there.

I'm not an expert, so consult a real expert in the field if you want tax advice.