You’re self-hosted, so you just need to do something like this:
cd /var/discourse
./launcher enter app
rake admin:create
You can enter your email address there and change your password (or any user’s password. It doesn’t have to be an admin).
Changing the Email address is harder.
Something like
./launcher enter app
rails c
u=User.find_by_email('old@address.com')
ue=UserEmail.find_by(user_id: u.id)
ue.email_addrress='new@fun.com'
ue.save
Might work, but that’s more of a hint than a solution.
Easierr would be to create another admin account, log in with it, remove admin privs from that account, change the email address, then make it admin again.