No direct keyboard support on the reMarkable, but you can trivially get a root shell over USB-C — while charging, unlike older USB OTG setups on phones and tablets with one micro-USB connector — so it’s totally something you can hack together.
None of the bundled software is designed for using a keyboard, of course, so it’s going to be just as DIY as the very earliest Linux handhelds. (Anyone else remember the awful HP “iPaq” PDA Linux environment? I set one up because I could, and them never see the device again because the UX and battery life were so bad.)
I’m less bothered about surfing the web on something like this.
When writing I find it easier to type and edit what I’ve put down.
Not sure if Remarkable has an optional keyboard or not but I think using a pen requires more thought overhead for me, if that makes any sense.