Some foreigners claim they have KakaoBank accounts, but they may be confusing them with KakaoPay accounts, or maybe the account is in their spouse’s name or whatever.
Suffice it to say: for foreigners without a Korean ID number it’s a definite no and with a Korean ID it’s a likely no.
And good news: they’re not called “ARCs” anymore. No more “Alien Registration Card” extraterrestrial stigma. Now it’s just the regular stigma.
I (living in SK for twenty years) do remember reading within the last year(?) that the government corrected the legal regulation that prevented foreigners from joining an online bank like Kakao Bank (it was a catch-22 situation, the rules required the bank to verify an account holder's ID using a system that only worked for citizens... the procedure to verify a foreigner required face-to-face verification with documents, but online banks by law were not allowed to have brick-and-mortar offices for customers to visit).
However, I have yet to read that any of the online banks have changed their procedure to take advantage of these changed regulations.
KakaoTalk, KakaoTaxi, KakaoBank even (bank obvs not for foreigners without local ID numbers).
The Kakao Metro map app is the best of its class too.