Thanks for the info on the mail forwarding service. I have a PO Box in the the US, that my sister or brother-in-law collect my mail from. My sister was able to pay the fee to renew it in 2020, but the PO clerk wanted me to pay in person, so I may have a problem renewing in 2021. It is good to know there are alternatives.
In case you did not know, USPS has a free service called "Informed Delivery". I get an email from the post office with a link that shows a black and white scan of letters or packages just before they are delivered. Occasionally I ask my sister to open the envelopes, take pictures of the letters, and send me the pictures.