How to temporarily disable iPhone SIM card?

It's easy to disable wi-fi connections or cellular data, but how does one disable connections to cellular networks? Three obvious solutions: - use Airplane mode. - remove SIM card. - explicitly set the network to a different carrier. The first also turns off wi-fi, the second is awkward and inconvenient, and the third burns CPU as it continually tries to connect to the wrong network. Is there an easy way to say that I want to use wi-fi without any cellular connection? (In case it makes a difference, this is specifically for an iPhone-8.)