Those are all interesting natural possibilities, but God’s Word makes it clear that Manna was something supernatural, and ended after the Children of Israel ate food from the Promised Land.
Joshua 5:12 (KJV)
And the manna ceased on the morrow after they had eaten of the old corn of the land; neither had the children of Israel manna any more; but they did eat of the fruit of the land of Canaan that year.
It first appeared after the dew in Exodus 16:8-14, not before, and not after Joshua 5:12.
Had it been the result of common insects, or nature, surely the Bedouins of the Sinai would have used it before, and after. And its doubtful the plants or insects would have produced the quantity and density necessary to feed such a large host - 600,000 fighting men plus women, elderly and children! The Word confirms it was not known before or after. Deut 8:3-16, Josh 5:12
It rained (or came) from Heaven Ps 78:24, John 6:31-32
It was found on the ground, not on plants. Ex 16:14
They kept some in the Ark and it was preserved, while the rest would go bad after one day, except the day before the Sabbath when twice as much was gathered for both days. Ex 16:19-20, 16:33, Heb 9:4
It was small, round, sweet, and would melt - Ex 16.
Manna sustained them briefly until they reached the land of promise. Jesus reveals that he is the true bread from Heaven that gives life!
John 6:30-38 (KJV)
They said therefore unto him, What sign shewest thou then, that we may see, and believe thee? what dost thou work?
Our fathers did eat manna in the desert; as it is written, He gave them bread from heaven to eat.
Then Jesus said unto them, Verily, verily, I say unto you, Moses gave you not that bread from heaven; but my Father giveth you the true bread from heaven.
For the bread of God is he which cometh down from heaven, and giveth life unto the world.
Then said they unto him, Lord, evermore give us this bread.
And Jesus said unto them, I am the bread of life: he that cometh to me shall never hunger; and he that believeth on me shall never thirst.
But I said unto you, That ye also have seen me, and believe not.
All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out.
For I came down from heaven, not to do mine own will, but the will of him that sent me.
Let’s not let God’s word get in the way here! < /sarc>
Amazing that folks here believe manna was supernatural (as do I) but that that which it prefigured, the True Presence of Christ in the Holy Eucharist, is only symbolic, in contradiction of the plain clear sense of scription of John 6.