Is it possible to make light/dark dynamic wallpaper be time-based without using the 'Auto' appearance?

[iStorm]

I've got a light & dark dynamic wallpaper (from here). I know the wallpaper will change automatically if I have my appearance set to 'Auto'...but I don't want to use 'Auto'. I want to be using dark mode (black windows) at all times, but still have the wallpaper change based on sunrise/sunset. I realize there is a time-based version one at that site that has extra images, but I'm only interested in the day and night ones.

How can I accomplish this? Is it possible to tweak the HEIC file so it is dynamic based on time instead of light/dark mode? Can I automate it some other way, even if I have to use the individual images?

 

[Slartibart]

I suggest you take a look into the Dynamic Wallpaper Club. There are additional ways to acchieve this, the technical info is given in their faq - basically you provide EXiF data (DateTimeOriginal, GPSLatitude, GPSLongitude) with your HEICs to use “sun mode“, or you just define a time-based schedule for change.