although occasionally business or specialist carriers require reactivation.

I would leave your old phone powered on until you're certain both numbers are working.

Things you'll probably need to do again.

These are the main ones.

Banking apps, Barclays, Lloyds, Monzo, etc.

usually require you to log in again or re-register the device.

Authenticator apps, depending on which you use.

Face ID for apps.

Apple Pay cards need verifying again.

Some car keys or digital keys may need reauthorising.

A handful of security conscious apps.

Things I would check afterwards.

Because I know your setup is a little more involved than average, I'd check.

Calls work on both SIMs.

Mobile data is using the correct SIM.

Wi-Fi calling is enabled.

Your free PBX ANA line behaves as expected.

Tailscale connects.

HomeKit accessories are visible.

Apple Watch has transferred.

Apple Pay works.

Your action button is configured the way you want.

I know you have it launching chat GPT live voice.