This query is about Kaivalya. Learned from the Bhagavad Vishaya kalakshepam that followers of the Sankhya religion and Kapilar tradition involve themselves in Kaivalya. It is also said they will be in Kaivalya for several yuga-s continuously. Are these people Siddha purusha-s?

Sankhya’s religion is misleading. As per the religious practices espoused by the Gita, after performing Karma yoga, while one is in Gyana yoga, one who desires Kaivalya, will attain it.
Siddhar-s are those who have perfected Yogam. There are eight types of Siddhi. The attainment of Kaivalya is different from the attainment of Siddhi.