Assuming you set up your account with Google from the start, the Bubble account should still have an underlying email account (and unknown password) associated with it.
First, try a password reset request using the email address of the Google account. Complete the password reset, and see if you are able to log in through that sequence.
I haven’t had occasion to test this, but I would assume that it should work.
I initially was just building some internal tools for my company and used my company email. But I have started building apps for a couple other businesses and want to convert my account to one I own and push the internal apps out to a separate account.