Btrfs is a great filesystem for proxmox in raid 1. Stop telling people not to use it
Btrfs gets a bad rap sometimes but I have been using it for years and it works very well. It is able to take failing hardware and power outages and still has good performance.
xfs. ext4 doesn't have a comparable feature set, and nobody is going to use those others as their main filesystems on Linux. bcachefs will be a contender, once it's included in the kernel, or if you're the sort who compiles their own kernels.