Porcelain Tile. is durable and non-porous, which means it will not absorb steam in the way that stone will. In fact, ceramic tile retains heat, so it acts as an insulator for your steam shower, keeping warmth right where you need it. In all, porcelain tile is an excellent choice for a tiled steam shower. https://www.arizonatile.com/en/blog/2018/june/choosing-the-best-tile-for-your-steam-shower
You would want something that will repel steam or any kind of wetness, porcelain will excel at this.
I agree that a porcelain tile is probably your best bet.
Hi. Consider using full sheets of Corian. It will be a breeze to clean and works great in steam rooms.