I agree that k3s is a great way to get started. You can easily bring new nodes online and upgrade them.
If you want your Services to behave a little bit more like physical boxes or VMs, where each service gets its own IP address (instead of using an ingress controller or service mesh, which are different beasts entirely), have a look at MetalLB. MetalLB allows associating an IP address on your home network with a Service, which is more or less exactly what you'd do with a VM or a Raspberry Pi.
Do you have any pointers towards how to get going?