Debian Stable, in my experience, can stay online for months, even over a year, with very little attention, and still work as well as you left it. You can also install RHEL or a rebuild, like AlmaLinux, RockyLinux, or Oracle Linux, as a workstation distro.
As for the device, my use case is fairly different so I'm not sure what to suggest. Maybe an Intel NUC, or a Framework laptop.
No distro I'm aware of still provides official box sets and CDs. Debian still provides materials for third parties to make them, though. Most of the vendors of pre-burned Linux media have also shut down, but one that seems to still exist (and offers Debian box sets) is https://www.shoplinuxonline.com/ .