Don’t use FreeBSD on a notebook.
Unless you can live without energy management, suspend, bluetooth, function keys and usable wifi speeds out of the box.

Is there any reason not to use Debian when you’re already happy with it on your main rig?

I would recommend Linux Mint. Yes it’s faster to update than Debian, but it doesn’t push the envelope nearly as fast as Fedora or Arch based distros.

Linux mint is just super easy, user friendly, you could use Mint without ever touching a terminal if you wanted. BSD would be a great pet project to fiddle with, but if you’re looking for a rock solid backup machine with zero fuss, Mint is perfect for that.

Not much use to go Ubuntu or Mint, unless you have specific issues with Debian that don’t happen with those. Even then, it may be one apt install away from a fix.

If you want to try out BSD, power to you. I wouldn’t experiment on a backup computer though, unless by backup you just mean you want to have the spare hardware and will format it with Debian if you ever need to make it your main computer anyway.

Otherwise, just run Debian!

If you want Debian with more frequent updates, consider going Debian sid. Base Debian is also fine, maybe with Flatpaks for more up-to-date applications where needed.

If by backup notebook you mean a notebook that you use in case your main notebook breaks or something similar, I’d install the same OS and software on it.

If by backup notebook you mean that you want to use it as a server where you store backups on, I’d use either Debian or AlmaLinux.

is there anything which actually bothers you about Debian? what impedes your workflow? what edge cases with hardware and updating affect you?

is there really a reason to switch? do you care about unburdening developers from dealing with systemD?

I’d go with Linux Mint Edge Edition (not the default Mint). Better support for hardware than either plain Mint, or Debian, and more optimizations for laptops and battery (ubuntu might be hated, but they have lots of kernel patches). Also, for some weird reason, Mint with Cinnamon uses less RAM than Debian with Cinnamon. Also, easier support for third party non-free drivers.

I love BSD, but I wouldn’t want it on a laptop. They’re just not optimized for such usage with batteries etc.

Simply install debian 12.5 again, the easiest choice.

Good choice.

Install linux mint, so I get ubuntu but without them throwing their subscription services down my throat. I’m unsure about other advantages, as ubuntu is debian based, maybe the more frequent program updates? Kernels are also updated more often than with debian as far as I know. Do you know of other advantages?

There’s LMDE, Linux Mint Debian version.

Go for FreeBSD: this might require a learning curve, because this is an OS I’ve never used. Are commands that different from debian?

Yes, commands are different (For example ifconfig and not ip. And watch on Linux is something different on FreeBSD) and you can expect several things to not work out of the box. Also, mounting removable devices is different. Documentation is very good though unless your reached a niche problem. I’d suggest to first toy around with FreeBSD in a VM (Qemu or VirtualBox) if you want to sneak preview it and learn more.

Go for FreeBSD: this might require a learning curve, because this is an OS I’ve never used. Are commands that different from debian?

Both of them are, at the very least, unix-like, so the core command set is mostly the same, albeit with sometimes large functional differences.

Simply install debian 12.5 again, the easiest choice.

You are familiar with Debian. This is probably the choice I’d go with.

Kernels are also updated more often than with debian as far as I know.

That’s why Debian has backports.

I use Debian on nearly everything that isn’t a “testing machine”…it’s just what I’m familiar with. Used to be like this with Fedora. If you are looking to just use it as a regular end user and don’t really need anything different or particularly want some new scenery, you might as well just install Debian again.

I wouldn’t switch to mint from debian. Freebsd could be worth trying, but I would play with it in a VM first. I am not knowledgeable about BSD’s, but there are others if you were unaware. They have similar names but I think netBSD and freebsd exist. FYI, BSD isn’t linux if you were unaware. Your phrasing suggested that you might think it is so I wanted to let you know.

Newer kernels are great if you need bleeding edge hardware or filesystems, but for your use case I really think debian is the way to go.

I would like to suggest you throw Fedora into the mix, or even opensuse if you want to try an rpm based distro. Opensuse has a leap flavor which is stable like debian. Fedora is fairly stable, but has regular releases (2 a year) so you also get more current software.

Sorry to throw more options into the mix, but those are fairly simple and mainstream options (fedora is more mainstream fyi) but they are worth considering.

Unless you’re specifically wanting to play with a different OS then Debian again. Makes much more sense to be using the same version of Linux and all the software ypu use rather than potentially different versions.

Also it will be simpler to maintain as everything is the same.

If you do want to play / test another distro then Mint has a low learning curve. FreeBSD is more different but you could easily try it and switch to something else if you don’t like it. Its different but not so much that linux users would feel totally lost.

Probably the most confusing thing for linux user trying FreeBSD is that Bash is not installed, and BSD uses sh instead by default. Bash can be easily installed and set as the default shell which will give a lot more familiarity. But otherwise it’ll feel like a familiar modern complete system, and you can use the same desktop environments you’re familiar with already in linux.

EDIT: You did say “backup” in your title. If that’s the main use case then definitely Debian again. If your laptop breaks or is stolen it makes sense to have a familiar system to pick up. Also important to sync and backup your data so it can be picked up on the other laptop. If backup machine is your focus then I’d say same OS and look more into data retention and retrieval between the two laptops, and ensure your important data is continuously backed up.

OpenSuse Tumbleweed, gets you on the bleeding edge and I have had 1 issue like 5 years ago where I got a broken xorg driver. Rolled back the patch using snapper/btrfs and was back in business. Upgraded like a week later and everything was fine. System is still chugging all these years later.

Also nothing wrong with running Debian Sid another distro I never ran into that many problems.

Linux Mint

Usually, I’d say silverblue but it sounds like you want to stay in the debian environment which is why I’ll recommend vanillaos. Just download the live image and check it out https://vanillaos.org/