ext4 on all hard disks, but my installs are all several years old at this point, and I might choose differently if I were starting over from scratch. The boot partition on the ancient laptop might actually be ext2; I don't remember and it's certainly old enough that that might still have been preferred Gentoo procedure when I first set it up. Removable media might be ext3, ext4, or vfat, depending on compatibility needs and how long ago I formatted it. If I buy an SD card or USB stick that turns out to be preformatted in exFAT, I reformat it before use to ensure everything can read it.

They're all solidly reliable filesystems (well, except for the vfat), but perhaps not the most featureful.

ZFS for nearly everything plus ZFSBootMenu EFI on root data pools. Get a bad upgrade? No problem, boot a previous snapshot (auto created with a pacman hook), which I had to do recently when 6.6.39 LTS kernel had a bug. Snapshots are also great when doing things such as upgrading postgres, hass, Plex, etc.

A combination of XFS and ZFS. I work in high performance computing (academic). While I love the reliability of ZFS for data archival and peace of mind that results provably haven’t suffered bitrot, sometimes I just need a 10 TB temp file(s) with fast mostly-sequential R/W. Appropriate selection of file systems lets me have both.

Ext4 bc of its speed for games and my main files. Btrfs on the root for compression

XFS on my server VMs and my laptops and desktops.

ZFS on my file server. I'd use it on my laptops and desktops too (and have done when I was using Xubuntu) but I've switched toFedora which doesn't come with a way to easily install with ZFS and I don't feel like jumping through hoops to get it done. And I can't stand btrfs. I don't know what it is about it, but I just don't like it.

Btrfs, ZFS and ext4. My servers use ZFS, my client machines mostly use btrfs and I have a sprinkling of ext4 partitions for specific workloads. I'm all in on CoW filesystems for snapshots, send receive, transparent compression and reflinks. I like btrfs on client machines and SBCs because it's easily available (baked into the kernel) and doesn't require maintaining dkms or holding kernel versions until ZFS supports them and because snapshot handling and other filesystem admin tasks are simple and straightforward. I run ZFS wherever data integrity is important, eg: storage servers and backup targets, but largely prefer working with btrfs.

Btrfs main boot drive

Xfs main storage drive

exFAT external "archive" drive (easy to connect to Windows machines if ever I need my backup in someone else's windows machine in an emergency and such)

Defaults

So Btrfs, ZFS and ext4 (ext4 is virtual only)

It's all Ext4, but I run SnapRAID on top of that on my data drives. I'm sure lots of people would tell me I should use ZFS/BTRFS instead, but I'm used to SnapRAID, and I like the idea if something goes wrong, I won't lose all my data.

I use bcachefs for my games, I like that it lets me have multiple disks with redundant data copies, plus ssd caching of frequently accessed files, this fs is linux specific for now as far as I know, and is still experimental. I use ext4 for everything else, and FAT32 for flash drives.

F2FS, because solid state and speed

Pretty much all ext4 except for a few Windows installs on NTFS.

We use btrfs for the / partition and xfs for any data partitions. Has served us well, the snapshot feature saves us some valuable time when an update goes awry.

Depends. Slower desktop machines XFS.
Standard desktop XFS, if it has a smaller SSD, Btrfs.
Home server ext4/XFS + ZFS. Generic servers at work ext4/XFS, backup/storage servers ZFS.
Database server, experiment with ZFS with compression enabled - ratio 2:1, but encountered problems (probably a bad HBA model), standard ext4/XFS.
Hosts with virtualization, small server - XFS, big server - ZFS (technically a ZVOL).

ext4, but the btrfs activity visible in the kernel changelog has slowed down recently after a long period of many bug fixes, so maybe I'll give it a try next time.

Servers - btrfs. Fewer layers of abstraction, easier to manipulate.

Laptops - ext4. I don't do anything weird with the onboard storage, plus it supports fscrypt.

Flash drives - exFAT. I usually need to access them on multiple platforms and exFAT is about as cross-platform as VFAT (but supports bigger files).

dual boot NixOS and FreeBSD on a single drive, ext4 on Nix and ZFS on FreeBSD. each partition has its own boot, swap and root, all encrypted

btw, OP wrote that FAT32 is limited, isn't it the default fs for the boot partition? can other fs like ext2/3 be used?

ZFS for my server’s root pool and main storage pool. Ext4 with snapraid for my media pool. Currently btrfs on my desktop and ext4 under vanillaos on my laptop (not sure if I could partition it manually to use btrfs but I’m considering that for snapshots)

Whatever my installation CD had as default 😂. I'm guessing ext4?

I use Btrfs for my root partition to be able to rollback if something goes wrong after update. XFS: in all other cases, since I hate the lost+found directory on ext4. Although I don't think there's any significant difference between ext4 and xfs in performance and reliability.

Btrfs for the compression and snapshots