I currently use TinyWall Firewall, it works very well, it’s small/portable, no complaints I even donated to the Dev but I would really prefer open source, also it needs to be user friendly like TinyWall so my non-tech family members can/will use it like they do with TinyWall.
Update: I just discovered that TinyWall is now FOSS, GitHub Link If a very powerful, easy to config/maintain Windows firewall that is also now FOSS is something your interested in, I highly recommend giving TinyWall a try