Alternative to Nook Glowlight Plus 4

I wanted to support an American company that isn't Amazon by buying the Nook Glowlight 4 Plus, but it's pretty clear that Barnes & Noble no longer really cares about the Nook. No dark mode available in the reader, no Windows program any longer so books can no longer be backed up, and a firmware update a couple of months ago has made sideloading on the device very difficult.

So, I'm now looking for an alternative with the following qualities:

• Not an Amazon Kindle
• Seven to eight inches
• Has dark mode as an option
• Can easily sideload ebooks
• Preferably has a flush screen, but this one isn't a deal breaker

Any suggestions?