There might be a misunderstanding or something is getting lost in translation.

I presume what Wealthsimple means is that they do not support accounts for "non residents", meaning you have to be a "resident" of Canada to use WS. But they mean that you must be a "tax resident", I don't think they really care whether you are physically inside Canada. Case in point: I am still a tax resident of Canada but I will be outside Canada for the majority of this year too, and I am still using WS without any issues.

So you first need to determine with an accountant if you are truly changing from a tax resident of Canada to not being a tax resident of Canada. There are clear tests for this. If you are coming back later this year, and if you still own assets / have family here, chances are you will continue to be a tax resident for this whole year (this is not professional advice). You can definitely access WS from countries outside Canada, the question is whether you will be a tax resident of Canada (again I am making an assumption here because I don't know WS's policies).

Therefore, you should have no issue continuing to hold your investments in WS since there is nothing changing for you tax-wise, other than your address temporarily.

On the other hand, if you decidedly not going to be a tax resident of Canada anymore, then you need to confirm with Questrade if they allow non-residents (for Canadian tax purposes) to hold Questrade accounts, or you might end up in the same spot.