+1 to koreader. I didn't want to install it on my Kobo because I don't really want to mess with the firmware of some devices like my phones and ebooks, but it's really a game changer when you get over the initial readjustment to the new controls.

The page turning feels snappier, the ui is better (subjective), and for me the killer feature is better dictionaries in different languages (which are present on the Kobo but not all languages). Not sure how it compares to the reMarkable2 ereader, but judging by the thread reMarkable's might not be even as good as Kobo's

Can this be installed on Remarkable?

Googling "koreader remarkable" gives back a pile of blogs, gists, reddit posts etc so I'm assuming yes.