One thing that will be the biggest general qol for your new build is likely to get a M.2 NVMe for your games and OS

Civ 6 is pretty flexible and dwarf fortress will run on a potato, basically anything remotely in the gaming market will play them fine. Civ 7 is more intense, but being turn based cpu tends not to be the bottleneck

Do you have any preferences (distro, cpu/gpu manufacturer, etc) and a budget? Most of the games on your list I am familiar with and will run on damn near anything remotely modern.

Lacing direction, with the fairly low requirements (from what i recognize), and assuming you are price conscious id suggest you poke around the used gaming PC market (either gamer friends, or failing that online), which will also completely bypass the tariff issue too.

PopOS is pretty solid for linux gaming and has a distribution specifically for Nvidia too which handles most of the headache with Nvidia if you go that route.

Whats your use case?

Was somewhat recently considering a linux laptop myself and ended up deciding the steamdeck fit my needs well.

A dock + portable keyboard & mouse for when i need to do typing or w/e, and a fun handheld console for when i want fun.

That being said, depending on what your “older” laptop is, it might not actually be much stronger, or it might be wildly overpowered for what you need.