"Kobo Libra Colour" eReader
I bought a Kobo Libra Colour eReader for ~$250 and, while it's not the cheapest model, it's one of my greatest purchase of the year.
I wanted to buy a reMarkable at first, but it is 2 to 3 times more expensive and I noticed that I don't feel the need to buy an additional pen to take notes on such a device. A regular $2 notebook or the Joplin application does its job very well.
The screen size is neither too small nor too big, and can decently show PDF files in landscape mode. The color feature is a nice bonus for covers or inside graphics, and also allows the screen to automatically "make the screen glow orange for nighttime reading" as they say.
It has all the basic features you may expect for an eReader: 32 GB of storage which is enough to put thousands of books. 16 GB would still be acceptable, but I don't mind additional storage. The page turning "speed" is fast and not an issue when you're reading a book at a regular pace.
You can drag-and-drop your files in the file manager of your operating system with a USB-C cable. Some versions of Calibre may work too to clean the metadata of the books you will upload (depending on the version of your OS though, Linux Mint not being up-to-date yet).
Last but not least, KOReader can replace the standard reading application if you need more customization. I haven't installed it yet as the built-in application is good enough for me.