With the advances in gaming on Linux in recent years, it is so tempting to switch full time. I would absolutely love to, but I am a Game Pass Ultimate subscriber and it is where I play a lot of my games on PC. I know you can use the cloud version, but I cannot stomach streaming games in their current state, so it is a no go. A large portion of my Steam library is compatible, but anytime I have done an install I end up giving in and going back to Windows for games.
I'm in the same boat. I'm ready to move over to Linux Mint, but I don't want to have to download my entire game and program library again because NTFS won't play nice with Linux.
If you don't mind doing it one at a time, and you've got a different drive besides the NTFS one (i.e. you're not just looking to just reformat the NTFS volume), this currently works:
Format the new drive with whatever, likely Ext4 or Btrfs
Install Steam and make a fresh library on the new drive
Copy the contents of the NTFS steamapps/common into the new steamapps/common (or copy the individual folders of whatever games you don't want to redownload).
Go into Steam, and act like you want to do a fresh install of whatever games you just copied over. Steam will act like it's going to start from scratch, but you'll get "discovering local files" before any downloads start.
Steam will either show the game as installed as-is or will update the delta to the current version.
I use this method also for restoring backups of games to an SSD that live on a mechanical drive.
If you choose Arch/Arch based, or choose to install one of its supported kernels, NTFS support is integrated into the mainline kernel since version 5.15
So you'd be able to use your already existing disk/partitions that have NTFS.
Of course you'd still need to install the OS in another partition.
I tried to keep NTFS around when I switched, but ext4 is much better for spinning disks and support for whole disk encryption (LUKS) is also another pro that made me switch everything after a while
NTFS is fine in Linux. I have a dual-boot setup for when I need to run or test something in Windows, and I use my Windows install drive as a Steam library in both. When I swap back and forth Steam occasionally does a file integrity check, but I don't typically have to redownload anything as far as I can remember. The only caveat is that if a game has both a Windows version and a Linux version I have to set my Linux library to use Proton for the game instead of the native Linux version, otherwise, yeah it'll see the files are wrong when I switch and redownload.
NTFS is fine with Linux, but any new OS tends to need you to install things again. There used to be a way to zip all of your Steam downloads for a new install, but I can't seem to find any instructions that still work.
I think the option is under Steam > Backup and Restore Games. I successfully backed and restored some back ups I had made about a year ago with that method.
I think you're right. I've used this before as well, but I was thrown because my Linux Steam only has "Restore Game Backup" as an option in the menu. I wasn't sure whether something had changed, or if this is a Steam for Linux peculiarity.