Here is a seed in which you spawn in a flat landscape. Only by walking a little further you will quickly reach a smaller mushroom biome. In this case the mushroom biome is quite flat compared to how they usually look like. In the mushroom biome you can find lava pools, ponds of water and even a mystic meteor crater.
A recommendation from us is to not enter the meteor crater as we haven’t had the guts to explore it completely yet. However, if you feel you got the courage to go for an exploration adventure inside the crater then please do so and let us know in the comments what you find!