The Punkt also has Signal: https://www.punkt.ch/en/products/mp02-4g-mobile-phone/

I think these are neat, but have an iPhone 13 Mini because it’s hard to beat Apple’s quality and privacy work.

I've seen those and have been tempted. I think I'd need two phones to pull that off. There are some things that require an iOS or Android compatible phone, e.g. most smart home stuff cannot be setup without a smartphone.

in the states, verizon has a number share program (two sim cards, one phone number). they consider the light phone a "wearable" and the monthly rate is similar to stand-alone data hotspots -- far cheaper than adding a "real" second phone to the plan.