No, Adinath and Shiva are not the same in Jain Dharma.

Very simple:

• Adinath / Rishabhdev

- First Tirthankar of Jainism. - A Siddha–Arihant: liberated soul who showed the path of moksha. - Not creator, not destroyer, not a “god in charge” of the universe. - His symbol (lanchhan) is the bull and he is always shown as a silent, meditating Tirthankar (no trishul, damaru, snake, moon, etc.). ( jainknowledge.com)

• Shiva (Mahadev)

- A deity from Hindu tradition. - Connected with creation–destruction ideas in that tradition. - This type of creator–destroyer god concept does not exist in Jain philosophy.

Why people get confused

• Both are sometimes called “Adinath” (first lord) in different traditions.
• Both are linked with a bull in pictures:

- For Adinath, bull is his Jain lanchhan. - For Shiva, bull (Nandi) is his vehicle.

• Some art shows both with matted hair, sitting posture etc., so from outside they may look similar. But in Jain view, they are completely different beings and concepts. ( jainknowledge.com)

Common Jain position (both Digambar & Shvetambar)

• Adinath = Rishabhdev = First Tirthankar of Jainism.
• He is not Shiva, not Vishnu avatar, and not any Hindu god’s incarnation. ( jainknowledge.com)

You can read a clear Jain explanation here