Adinath Bhagwan (Rishabhdev) did not worship any other deity to attain Keval Jnan.

In Jain Dharma:

• A Tirthankar becomes kevali (omniscient) only by:

- his own purusharth (self‑effort), - destruction of karmas through tapas, samyak darshan, samyak gyan, and samyak charitra.

• He may have done bhakti and spiritual practices in his earlier lives, but not as “worshiping some higher god who then grants Keval Gyan.”
• Jain Siddhant clearly teaches:

- No creator‑god gives Moksha. - Even Tirthankars attain liberation by their own effort, based on beginningless karmic purification and right practice.

For Adinath Bhagwan specifically:

• He performed very deep tapas (austerities) and dhyān (meditation).
• Under the Vata (banyan) tree at Prayag (Purimtal), he attained Keval Gyan, purely by his own spiritual effort and complete destruction of gyanavarniya, darshanavarniya, mohaniya and antaraya karmas. ( jainknowledge.com)

So, the clear Jain answer is:

> Adinath Bhagwan did not worship anyone else to get Keval Gyan. > He realized his own soul through self‑effort, austerity, and meditation, and thus attained Keval Gyan.

You can read more about the place connected with his Keval Gyan here