I absolutely and utterly swear by my reMarkable 2.
Large enough to display pdf's without having to scale down (which always messes up the page readability), can take notes right on the pages, even in multiple layers if I want, can draw on top, include overlays, export my notes as text or even save them within the pdf itself, etc. etc. etc.
Coldest was -44°C when I was working as a northern lights guide in Norway. We'd always take our tour groups to areas with a high likelihood of polar activity, and once the whole coast was widely overcast so that we had to drive almost to the Finnish border. Camped out along the road towards Kilpisjärvi coming from Skibotn (company was based in Tromso).
Hottest was +45°C in Lagos, Nigeria. Used to work there as well for a good while.
There's a companion app (Android and iOS) and a client software (Windows and Mac). They sync the reading progress as well as notes, so you can always take the version from your PC and print it with all your notes in place if needed.
The software only works as a reader though, so you can't edit anything there. If you do use it to read on, it syncs the current page you're on back to the device though, so at least you can read continuously.
The only real issue I have is that searching for communities I know exist on other instances often fails, and opening them in their home instances doesn't offer a subscribe button to my host instance.