You most likely aren’t going to be able to retain timestamps unless you permanently keep a Windows partition. Linux uses a different drive format and permission scheme. Structure, absolutely; timestamp and owners and other little Windows things, not realistic.

Also unless you back stuff up you run a risk of losing it. No way around that period.

The gist of what you’ll do is resize your Windows partition, create a new partition for a Linux install, and mount your Windows partition in Linux until you’re able to move data over. You probably want to dual boot at least until you’re sure Linux can properly access the data you need.

Useful links

• https://unix.stackexchange.com/questions/312424/how-to-install-without-loosing-any-data-in-my-hdd
• https://superuser.com/questions/821131/is-it-safe-to-resize-windows-partition-with-gparted
• https://wiki.archlinux.org/title/Dual_boot_with_Windows

I don’t have a second internal drive, so I’ll probably use an external hard drive or cloud storage.

Best to get both. Two copies of the data is better then one. Ideally have three. One being remote is also a plus as that will protect you in case your house burns down or something else drastic.

1.What’s the best way to back up and restore my data safely while preserving all metadata?

There is no real best way. Loads of things can be used to achieve the same purpose. But there are two main end goals: either copy/sync the data with a tool that can preserve timestamps or use a tool that can archive the data into a single file (that can optionally be compressed - like zip). Or for cloud providers they typically have their own tools that can do the syncing for you and will typically preserve timestamps by default. Just find one with a sync tool that also works on Linux.

There are loads of backup tools for windows that can do these things - though you should use one that does not use its own propriety format but instead something more open that can be read from the Linux side. I don't use windows these days so cannot advice on what the best tools here are.

Otherwise you can do this from a Linux Live USB using Linux based tools. If you are fine with the CLI then a simple way is to just mount the drives and use the rsync cli utility to sync the data you want across. rsync also lets you cancel and resume the sync which can be handy for larger directories. Or use the archiving tool tar to create a archive of the data on the other drive (this can be optionally compress). You should be able to use the filemanager to create archives as well which might make things a bit easier and should preserve timestamps - but just copying the data in a filemanager I don't think tends to preserve timestamps though so best to use the CLI for that or a dedicated tool.

What ever you decide to do test it on a small folder first and see if it does what you expect/want it to before committing to copying large amounts of data.

3.How can I access or use files that are only supported by Windows once I’ve switched to Linux? Are there workarounds or compatibility layers?

This depends on the file formats you care about. Some things are already supported by native Linux programs, others are not. Some windows only programs can work in compatibility tools like WINE - but I would only do that as a last resort. Personally I would figure this out before you reinstall your system. Start by finding Linux friendly programs for the files you need to use and see if they work with the files you want - if not try converting them before switching. Most Linux programs can also run on Windows so it is best to find these alternative and test them out before wiping your windows install. You can also boot up a Live USB and check things that way before committing to a install and wiping your system.

You can also (in addition to backing things up properly) buy a new SSD for your laptop and swap them around - keeping the original install in place in case there is something you forgot or need to switch back to access some old program you didn't think about.

I have about 300GB of personal data on the system

That's a lot of porn!

First thing to do is to prune the data and remove what you don't need. Be brutal (it really takes practise).

You should always be running a backup process, something automated. And be verifying it at least once a quarter by restoring some files.

https://www.backblaze.com/blog/the-3-2-1-backup-strategy/

I bought a second SSD and did my clean install there. You can also get an external case to put your old drive in and just copy from one to the other. There are other hardware solutions but that's probably the most straightforward.

The files themselves should work just fine as long as there is software to open them. Libre Office will open MS Office (that end in x like .docx) files just fine, for example. There is an installable compatibility layer to run windows software, Wine, but everything doesn't necessarily run perfectly out of the box.

I've only tried one thing (a game) and it needed some video options set that I only found on the forum of the game developer, but worked flawlessly after that. I can't really speak to compatibility beyond that but I expected it to be a lot harder than it was. AAA games and multiplayer games that use rootkit anti-cheat I think are the least compatible. If it's mainly office software you're interested in I would prefer native Linux myself, and I haven't really tried them anyway.

Some others might be able to steer you better but maybe the perspective of someone else who made the switch and somehow made it work will help.

1. are you currently regularly backing up your data? If so, use that. In case everything goes tits up, you'll need a Windows box to restore that (unless your tool can also work on Linux). Now, if you're not using a backup tool yet, you can either choose one for Windows now or accept some metadata loss and carry on with #2 below.
2. I'm assuming for this question you mean a tool to transfer data between your installs. Most data compressors will store creation and modification times and folder structure. Some can store owners, but that will be useless in your new Linux install. What other metadata are you talking about? Photography metadata (ISO, aperture, etc) stays in the file, not outside it on the filesystem. So if you're satisfied with that, I'd recommend 7zip. Add your important files to an archive on an external hard drive.
3. If you mean Windows partitions, don't worry, those are fully supported in Linux. If you man individual files, it's more complex to explain, but not a cause for worry. There's nothing inherent in a file that ties it to a particular OS, with the exception of applications (executables). So what you have to look for is what Linux applications can handle the particular file type you're interested. Failing that there's Wine/Proton. You know the Steam Deck? It's a Linux device running Windows games through Wine and Proton, which are compatibility layers. It's no silver bullet, though, some apps don't work well or at all.
4. Bonus A: for backup on Linux, it's hard to beat Borg. Vorta is a great GUI for it. Easy to set up, is remarkably fast, and compresses data really well.

Boot to another linux machine, back up your files with cp -Ra /path/to/old/data /new/backup/location and it might keep your timestamps. Some exe's you can run with wine, but not all of them. msi are installer packages and I don't think you can use those. If those exes or msis are games, try adding them to steam as a non-steam game.

To answer your questions:

1. Since this is a one-time backup, the easiest way is to copy your files to the external drive, install Linux, then copy them back to the SSD. I don't know if it's possible to preserve the Windows metadata though since that data isn't stored in normal, user-accessible files. Folder structure will be preserved though, and you can keep the same creation and last-modified dates using the cp command with the --preserve option.

2. The normal file copy/paste commands will work fine. If you want to do periodic backups, look at rsync.

3. LibreOffice will open most Microsoft Office files, and Linux has many FOSS alternatives to common commercial software. You can also look at Wine to run native Windows programs under Linux.

https://forums.linuxmint.com/viewtopic.php?p=1552802&sid=b71206a65b47e7f0f57ee4e526031e3d#p1552802

I personally use syncthing and sync it to a nas (with btrfs snapshots), I used to send it to a raspberry pi

A long time a go I’ve used LuckyBackup a gui over rsync to copy and overwrite to an external disk.

If you want to keep your dara safe, back them up. You should have done this all the time. That SSD isn't going to last forever. I could give you advice like creating an extra partition concentrating your data there and keeping it during the install but you -correctly- asked how to keep your data safe and there's just one correct answer: back up.