Linux

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.

@Psyhackological
Work stations all run Ext4.
Main server: Ext4 on main partition, ZFS RAIDZ2 on the data.
Secondary server: BTRFS on main, BTRFS RAID1 on data.

If BTRFS could natively encrypt and had stable RAID6, I'd be using it probably on everything.

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

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.

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)

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.

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've been basically using btrfs on a lot of my disks because of the features it has.

Before I switched to a borg based system, my backups partition used btrfs for compression.

My main OS disk is btrfs so I can use timeshift snapshots, which are really worth checking out if you tinker with your system a lot.

I have two more btrfs partitions software raid0'd together for my steam library, nix store and other big but loosable things.

And my main home folder uses btrfs because I think the checksumming thing it does is more reliable for error detection, and cow is more fault tollerant on power failure?

... And I now fell like I'm one of those people with an over engineered storage solution. I just never get rid of old ssds or hard disks!

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.

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.

NTFS Usally for windows,ext4 for linux,btrfs to install linux on,vfat/fat32 for cross platform compatibility

Btrfs because it sounded cool when I first read about it and worked fine so far :3

Btrfs for the compression and snapshots

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).

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).

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

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