Ghamdi Sb define sunnah as the ritual done by all prophets. As far as I know, by this defination its not sunnah.
There is famous narration considered as sahih
‘Umar ibn al-Khattaab said, when he kissed the Black Stone: I know that you are a stone and have no power to harm or benefit; were it not that I saw the Prophet (saw) kissing you, I would not have kissed you”
It shows that its not obligatory to kiss it.
Beside the black stone ws stolen for more than 20 years. It was not a short period. As history books mentioned it was broken into peices as well.
The hadeeths about black stone being hand of Allah, or place of weeping etc are mostly zayif as classified by Shaikh Albani