It’s possible to get a 'forest 'running on a phone, so you have some way to go 
Some ideas:
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Lower poly meshes.
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Smaller number of meshes ( I don’t mean in total, I mean the less you are instancing, the better ).
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Occlude areas using height changes in the landscape, also possibly large rocks. It makes a more interesting map also.
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I assume you’re not using Nanite.
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Simplify the ground material.