As an aside, that site was data breached at one point in the past because the unique password I used there got out on haveibeenpwned so theres that...
Interesting - have you got any idea when?
I have used a unique email address for my 68kmla account since 2019 and it is not in haveibeenpwned's database, so either it was before that, only a partial leak, or they got your account details another way. You haven't ever had a Yahoo email account have you? That has always been the biggest perpetual breach of personal information.
By the way, this thread is public.