Same issue as most people in this thread.
Just adding my name to this thread to desparately try to indicate the scale of the issue to Jagex.
Same as many others in this thread: Issue affects one of my accounts, other accounts work as normal. Account is affected on regular IP address, mobile data IP address, every VPN IP address I've tried, nothing helps. OSRS mobile works on the affected account, steam login to RS3 works. Desktop official clients for RS3 and OSRS (and also RuneLite) give the "too many login attempts" error.
I have done everything on the Jagex support article, very unhelpful.
16-Jan-2021 22:56:57