I run a cluster on 3 nucs. You could also do it on one nuc, or any other machine. Nucs aren't discontinued, they're just owned by Asus now.
Fair warning that going from zero to fully-automated-setup ansible+k3s+flux+rook+nginx+cloudflared is both very confusing and not very educational
I started with that template and ran into issues that were like 5 layers deep in infrastructure that I'd never touched that was auto-deployed and ended up just starting over from scratch. The final product from the onedr0p template is super slick but there's a lot there and you don't get any chance to understand it one piece at a time really.