I am trying to change my password on the forum and keep getting redirecting to the “My subscriptions” page.
If you go to your my.avast.com account and add the email you want to your list of emails. You should get a validation email (I think), once validated you should be able to change that to your default email. This I believe would then be your email address for the forum also.
You don’t say what Avast Program your are using, Avast Free or one of the Avast Paid versions ?
The reason I mention this is, with paid versions your subscription is also linked to your email and that may be why you are being forwarded to your subscriptions page. What I don’t know is how this could effect subscriptions linked to that other email.