It would be helpful to create a webpage which shows where you can buy hardware which comes (even optionally) with Plasma preinstalled.
- Pine64
- Pinebook: KDE Neon by default AFAIK, but out of stock (100$)
- Pinebook Pro: Mate, but there's a image with Plasma (200$)
- Manjaro
- Bladebook: apparently out of stock, should have Plasma option (350-420$)
- Spitfire: website does not work? (1000$)
- Zareason
- Ultralap 6440: Kubuntu option (1000$)
- Verix: Kubuntu option (1700$)
- configurelaptop.eu: clevo computers with Kubuntu option
- ubuntushop.be: has something that can use Plasma, but I can't understand how does the website work
- Tuxedo: "For advanced users and selected devices we also offer ... KDE plasma"