As a Montessori mom of a 7yr old, it really doesn't matter to be honest. To caveat that, felt can get nasty as a toddler will likely mouth the crap out of it and washing felt thoroughly is kind of a pain in the butt.

I bought my daughter a recycled plastic (high quality/thicker materials) food/kitchen play sets from Target when she was little and she STILL plays with it. Even outside and for science experiments. We've added some Melissa & Doug items over the years that are wood & plastic; her favorite is the ice cream set. She also makes food with her playdough, "cooks" it in her kitchen and serves it on the plastic plates. It's fun to see her be creative and combine materials.

Don't get hung up on the notion of "Montessori approved" materials and such. It's the concept and approach that matters, not specific materials. Allow yourself to be flexible and get behind the intent of what you're going for rather than having the "right" materials. Mix it up a bit and see what inspires her!

Edit: Green Toys is the brand for recycled plastic toys. This tea set has survived 5ish years now.

I’m not an expert on toxins but the ikea play kitchen is mostly wooden. Very minimal plastic. It’s quite sturdy but you can anchor it to the wall for peace of mind. It’s also affordable (compared to other kitchen sets) and there’s lots of inspiration online to jazz it up if you’re so inclined.