In Jainism, the difference is:

Keval Darshan

• The pure, total, unobstructed perception of the soul.
• It means the omniscient soul directly perceives all substances, modes, and realities in their true form.
• It is the state of complete darshan without any ignorance.

Keval Gyan

• The pure, total, unobstructed knowledge of the soul.
• It means the soul fully knows all substances, modes, and realities in their true form.
• It is the state of complete jnan without any limitation.

Simple difference

• Darshan = direct perception / seeing / awareness
• Gyan = clear knowledge / knowing / understanding

In spiritual meaning

• Keval Darshan is the complete, perfect perception.
• Keval Gyan is the complete, perfect knowledge.
• In the state of kevalin, both are present in their pure form.

Very short summary

• Keval Darshan: pure seeing
• Keval Gyan: pure knowing

If you want, I can also explain the difference between mati gyan, shrut gyan, avadhi gyan, manahparyay gyan, and keval gyan in Jainism.