Also curious what Linux distro and desktop you're going to. Flatpak makes it matter a lot less these days, so long as the base stays pretty current.
As for Linux distros. The MNT Pocket Reform comes with Debian and I plan to leave it at that even though Debian is not my favourite. I will use Niri and Noctalia with it. I plan to make use of whatever Debian package but if it is too old for my taste, I'll look for AppImages and Flatpaks as needed. I got a Surface Go 1 running exactly that setup but with Fedora and works really well for me.
Want to use KDE Connect to link whatever Android I get with the laptop.
Also, it seems relevant to mention that the software is mostly maintained by a Chinese company (T2Mobile), which might be relevant depending on your threat assessments.
For security/software updates it's pretty much:
GrapheneOS > iOS > Pixel OS >> Samsung flagships >> pretty much everyone else.
Absolutely agreed about the gatekeeping — just as example, you cannot even update your MacOS without being online unless you create a full USB Installer.
For your particular situation, presuming your hardware supports it, you can use MrMacintosh guides [0] to downgrade your OS from Tahoe — I recommend the latest Sequoia installer — all officially downloaded via Apple links.
[0] <http://www.mrmacintosh.com>
I further recommend blocking *.apple.com & *.icloud.com (and many more hosts) using a PiHole (so simple, so necessary).