I did not update my ReMarkable 2 for years either and had probably the same clock issue. There was an article on the FAQ website from remarkable, if I remember correctly, that took me to a step-by-step process by which I could update it. Don't remember exactly how (I think I had to use the cable and connect to PC; which normally is not needed) but let's just say even if at first it seems like it doesn't work anymore and you have to hack it yourself, it is not actually needed. Nonetheless, this hackabality is the main reason I got mine (although I don't hack it, the optionality and thus probable longevity made the difference in my buying decision. I do not regret.).