Hi Natalie,
Some great ideas above. One tangential thought — Would there be photos in your portfolio that could be appropriate (have required permissions) for stock imagery site? Also images of the city in lockdown on your walks could be a resource for news sites / channels, potentially.

Also surprising some existing / old clients with a photo from their shoot, not included with their original package could bring a smile back and you could be sure they come back to you when they want pictures taken.

Stay well,
Priti