Is there any natural remedies for a mucocele on rim of lower lip? Evening primrose? Salt solution?

Not really. Usually they will not respond to otc or home remedies. A minor office procedure will easily remove it. That is your best solution.
Mucocele elimination. I am not aware of any, & these would only perhaps aid in a reduction of inflammation. The pathology behind a mucocele dictates that almost 100% of the time it will repeatedly present itself & require excision. If anyone has a successful, evidenced-based natural remedy i would be interested to know about -as the founder of the nation's first fully sustainable & eco-friendly oral surgery facility.
Mucocele. Simply put alum on the mucocele and let it set for around 10-15 minutes. Follow up with listerine for 2-5 minutes. Repeat this every day until the mucocele has resolved.