I didn’t see many 7-8 inch tablets with dual boot, 4GB ram and the resolution you are looking for. For this size of tablet you will have an issue with the battery. I believe Jumper was with this configuration on eBay and Aliexpress although maybe 720p resolution and standard USB.
If you want all these figures you list you may need to go for a 9-10 inch tablet. More choice and quality – e.g. Teclast.
You wont get 4gb sadly. Full laminated and windows Mi Pad 2 – Windows version also has 64gb storage, great screen, usb-c and a pretty decent chipset. Only downside is no microsd. No idea if it can run Linux. Perhaps you could just run a virtual machine, like hackers do on phones?