I was watching a video ,where a guy run his home selective loads after power outages because of Hurricane Milton. I think North American Continent must start wiring residential units on two panels in order to address this in more effective methods
Service panel can have all the heavy loads like Cooking Range, Heat Pump, Cloths Dryer etc. and all lighter loads essential circuits must be wired on secondary panel. Small induction heater or gas cooktop can be used for cooking in such emergencies.
That way one can turn off breaker for secondary panels from service panel and run all lighter loads on generator or Off grid Inverter safely in case of power outages.
It is always recommended hire a certified electrician. If you are sure you have the knowledge of the subject then this might help you in making your decision. With the existing wiring you can shut off Main breaker of service panel and lock it in off position. Switch off and lock all double pole breakers greater than 20 Ampere rating. Switch all other breakers in off position. Now you can feed the power from generator or off grid Inverter using the right wire gauge and appropriate overcurrent device. Now you can turn selective lighter loads like lights, fridge, Gas heat furnace etc. Make sure total loads you run is less than or equal to the generator or off grid inverter power ratings. Check Table number 2 in Canadian Electrical Code Book for ampere rating of feeding cable and use right size overcurrent device to feed through.