I can't find a way to just change my email address on my subscription. How do I do this?
Changing the e-mail address associated with an account is not currently supported; you'd need to create a new account with the desired e-mail address, then use the "Replace Admin" feature on the hub to swap out the registration:
However, it sounds like you have an active subscription. You'd need to cancel that and wait for it to expire (although Support can do some magic to work around this if you have an exceptional case), as subscriptions are tied to the hub's admin account.
Additionally, your Community e-mail address can be changed in your profile -- not required but probably also something you'd be interested in doing to match.
So I need to buy a new subscription, wait for it to expire (8 months from now) just to change my email address? My existing email address will be gone in a month, that is why I am changing it. I don't want it to around for 8 months. Surely there is a better way.
No, losing access to your email account would be an "exceptional case" that I referred to. Submit a support case here: Subscriptions – Hubitat Support
I didn't say this, but no, and I would not recommend purchasing anything on your new account until the old one is figured out.