Linux

you already stated both options, there is no option #3. snapdragon support isn't there yet, you'll have to make do with Intel and AMD options; for the stated use cases, even 5-year old models will serve you plenty. ideapads, thinkbooks, whatevers are consumer-class models and shouldn't be gotten used (not even new, in my opinion) as they have nothing in common with T-series thinkpads.

if you'd like to hang on to your hardware for longer, go with the T14 (no S-suffix) as those things are easily expandable, serviceable and cross-generation compatible (same docks etc.).

X1 Carbon is awesome specs and has that lightweight portability element.

Both the T14s and X1 Carbon would be good options. I also have an x390 which I quite like.

I would suggest holding off on buying an ARM laptop specifically for Linux at the moment (maybe not too long from now though). Although there is an increasing amount of support, it's still not fully there, and there is most likely going to be quirks here or there that can throw some issues you would rather not deal with on a daily driver machine (e.g. having to extract firmware from the Windows partition in order to get some features working for the Snapdragon devices). Probably your best combination of power efficiency and performance on x86 at the moment will be something like the Ryzen AI 300 series CPUs. If you like ThinkPads, I would suggest the Ryzen version of the T14s Gen 6, which is essentially the same as the ARM version bar the CPU. I've been using a P14s (very similar to T14s just with some tweaks as it's marketed for mobile workstation users) Gen 5 and even with the lower capacity 39.3Wh battery (compared to the 57Wh battery you can get on a Gen 6) I've easily been able to get 6 or 8 hours in the balanced power profile with ~70% brightness on Fedora, so probably the T14s Gen 6 can do 10 or 12 hours on a charge.

The Linux support of Snapdragon SOCs for desktops and laptops is unfortunately severely lacking. Qualcomm pledged to provide upstream divers, but then the Windows drivers turned out to be a mess and the Linux version had to wait. It is nowhere near production ready. Most of the hardware enablement work is currently as far as I can tell being done by German OEM Tuxedo Computers because they are working on a Snapdragon powered laptop that ships with Linux. But even their work was impacted by Qualcomm stalling (the linked blog article lists Christmas 2024 as their target release date and that didn't happen).

I'm also making the slow transition from Apple to Linux, and I (relatively) recently bought a Framework 13. I went with kind of a minimum-specs loadout, figuring I didn't really know what I was getting into and I could upgrade it later (the primary selling point of Framework). I've been satisfied with running Fedora/Gnome on it for several months. I get the impression that the distro is more important than the hardware in terms of having a comfortable MacOS-to-Linux experience. But because Framework explicitly supports Fedora, I felt like it was a smaller step away from the walled garden, "it just works" experience of being a Mac user team just going straight to a distro and manufacturer that was likely to require a lot more manual setup and knowledge.

Even their new Ideapads with the AMD APU's (8845HS) are awesome and great value.

Framework

To just directly answer your question, it seems the T14s is the best supported.

Ubuntu supports it in Ubuntu 25.04 but it does not look like there is support in Fedora yet.

You will probably have to install KDE yourself but it should work fine: https://linuxconfig.org/kde-desktop-installation-on-ubuntu-24-04

If you have access to China only laptops market, the Lenovo ThinkBook 14/16 + Intel Core Ultra 7 255H are very capable all-in-one laptops that you can run an eGPU via TGX(Oculink) in a CPU that is tuned with 70w that you can't get with the Thinkpads, maximum is 55w.

I'm assuming you're familiar with Asahi Linux?

It's still very much a work in progress.

https://asahilinux.org/docs/platform/feature-support/overview/

At the moment I'm bridging the gap by using homebrew, UTM, ssh into local hardware and shortly remote desktop on EC2.

It's far from ideal, but that's where I found myself after my x86 iMac died last year, so I feel your pain.

I'm following the progress of nixos on snapdragon, but its still a bit early for me. Audio kind of working but might damage your speakers, webcam not working, crashing on 64G version but not 32G, etc. Also some funny business about needing windows for firmware or something. These issues are getting resolved but aren't completely solid yet IMO.

Don't know where things stand on the more mainstream distros but I'm guessing its probably similar.

any Thinkpad is fine. My E14 Gen2 is very good with Ubuntu

you can just install Linux on your "Apple Silicon-MacBook"

Have a p14s (older gen) and it runs very well on linux. Im running fedora which lenovo sells prepackaged so you get firmware updates and bios updates through rpm. I would say any linux Thinkpad would be a solid choice. I would just suggest getting one without soldered ram so you can upgrade or repair. Also check the panel brightness too because my display is shit.

Are you planning to run Linux on it? Dont get a snapdragon then. Its not ready yet and youll have a ton of issues.

https://en.wikipedia.org/wiki/Lenovo#Superfish

Just buy a laptop, stop trying to complicate the process. The great thing about linux is that it runs fine on almost anything.