Iron Brigade is a weird action/tower defense hybrid seasoned with typical Double Fine craziness.
I haven’t tried the multiplayer mode, but the campaign works perfectly with Proton.
My specs are:
Distro: Ubuntu 19.10
CPU: Intel Core i7-8700K @ 3.70GHz
GPU: NVIDIA GeForce GTX 1080
GPU Driver: NVIDIA 440.59
RAM: 16 GB