What's a good choice for a second hand nook🤔

[Scoob]

I'm looking to add another symmetrical button ereader to my line up with a budget of 30$. I'd like it to sideload books as simply as it is to do with my Kindles. If it helps, I use Calibre on Windows 10 and am decently tech savvy. Moreso if I have directions to follow. I am undecided if it needs to have a backlight or not. Storage wise I always like to have most storage possible on my other devices but I'm in the dark when it comes to e readers. Also preferably a device in the 6in size please.
Those are really my only parameters but feel free to tell me if I should be asking more things to get a better pick. I've never used a Nook before but if the software or reading ui has quirks that's okay.