Maybe clarify if you are already in Canada which maybe assume you are if talking landing appointment which by the way have all been cancelled until currently after April 13th.
Personally and I have no inside information I would suspect that flagpoling would be treated same as arriving at a POE as far as restrictions go given technically you leave Canada and come back. CBSA already never come across as being keen for flagpoling so COVID just adds to their case.
IRCC has special process for people whi cannot travel/land with their COPRs
https://www.canada.ca/en/immigratio...t-residence.html#Approved_permanent_residence