As the title mentions - How can I change the ownership of a Google Play Console Developer's Account?
Change the ownership means to associate the developer's account with a different Gmail account & let the previous association be let go off (and possibly not pay the $25 USD registration fee again).
Note: There is a similar question asked but I think it's incorrectly marked as a duplicate of a question which doesn't answer the question. (It answers How to transfer apps to another account).
I also beg to differ that the accepted answer also doesn't seem to answer the question.
Hence, asking & answering this as a separate question for the future readers.
You cannot change/transfer the ownership of a Google Play Console Developers Account.
Once a developer account is created, the email address used to register is permanently tied to the account.
Account owner email address and country
The account owner email address and country can't be changed. However, you can create a new account using a different email address or country and transfer your apps to your new account.
Accounts with published or unpublished apps
To transfer apps to a new account, go to our app transfer checklist.
Accounts without apps
If you haven't published any apps using your existing Play Console account, you can create a new account and cancel your existing account.
However, there is a workaround.
References From official Help Docs:
Step 1: Make sure your Google Play Developer accounts are registered & active
Before our team can transfer apps from your original account to a different account, known as your target account, both Google Play Developer accounts need to be fully registered and active.
Note: You need to pay the $25 USD registration fee for both accounts. After the transfer is complete, if you want to close your original account, our team can refund its registration fee.
Use a different account for your developer account
If your developer account is linked to your personal Google Account, consider creating a new account to use for your developer account. This way, if one account is compromised, the other account can still be secure.
If you’ve already registered, our support team can transfer your apps to a new account. To transfer your apps to a different account, register a new developer account, then prepare and request the transfer with our support team.
Note: If you close your old account, we will refund your original $25 registration fee.