No, you cannot link enterprise and personal accounts because they use different user authentication.

Proof by cases:

Case 1: Attempt to link enterprise/personal via enterprise account.

Sign in to <enterprise>.github.com via LDAP. Upon sign in, select top right pfp button --> Add Account

Redirects you to enterprise sign in, personal account credentials invalid.

Case 2: Attempt to link enterprise/personal via personal account.

Sign in to github.com. Upon sign in, select top right pfp button --> Add Account

Redirects you to non-enterprise GH, enterprise creds invalid.

Try to get around it and get back to me if you do. Would love to show (obfuscated ofc) my enterprise work on personal in pursuit of that full green graph.