Which is/are correct and why?
- Der Hund ist mein.
- Der Hund ist meiner.
My thinking is that only 2 is correct. If a noun follows mein-? then it's a determiner, and the masculine possessive determiner is mein. (See the inflection table here.) If a noun does not follow the mein-? then it's a pronoun and the masculine possessive pronoun is meiner. (See the inflection table here.)
On the other hand one grammar I looked at said there is a special uninflected form mein used specifically after sein or similar verbs. So dieses Haus ist mein not dieses Haus ist meins. Another grammar I looked at seem to agree with my reasoning. DeepL allows both versions and the DWDS usage database has examples with both variations:
Du bist mein. ("Game of Thrones" The Prince of Winterfell, 2012)
Du bist meiner. (Transformers 3 - Die dunkle Seite des Mondes, 2011)
If either version is a allowed, is there a difference in meaning? If it depends on circumstances, which version is used when?