My ideal ecosystem would be having a Fairphone 5 (Postmarket OS) paired with the Pinetime Watch, the Framework Laptop (Linux Mint), the Steam Deck, the AMD desktop (Nobara) and the openwrt router.
The services I would use would be Lemmy, Wikipedia, Mastodon, Organic Maps, LibreOffice, Ecosia, Loops, Librewolf, Thunderbird, Friendica, Pixelfed, Proton, GOG, Peertube, Matrix, Localsend, Gitlab, Kiwix, Audacity, Gimp and Bookwyrm.
I did forget to mention something, provider support.
USA: Verizon doesn’t work due to Verizon whitelisting devices. From what I have heard, AT&T and T-Mobile both work.
Australia: The situation is quite complicated. Due to the ECS determination, MNOs and MVNOs need to block phones that they can’t verify can make calls to emergency services via VoLTE. As a result, Optus and MVNOs that use Optus have started blocking FLX1 phones. Telstra definitely still works, with multiple MVNOs confirmed to be working. But who knows for how much longer. Not sure if Vodafone (Australia) works or not. This mess in Australia is solely thanks to the Australian government. I do have faith that it will either continue to function on Telstra or, if blocked, can be made to work again in future.
Not sure about any other countries at this point, these two seem like the biggest concern at the moment from what I have read in the Telegram and forum.