It all depends on the amount of devices you need to migrate. For me the best solution was to start over (27 devices). Took some time but it was a blessing when I managed to get new ones in.

From HA Forum:

Ok, just decided to pull the trigger. Based on my experience…

Go to the configuration on your current ZHA. Select “Download Backup” to get a current backup saved somewhere. Select “Migrate Radio”. In the next section tell it you want to change devices. It will wipe your old device and tell you to unplug it. I unplugged my old device and plugged in my new device The process asked me which device I wanted to add and I picked the new Sonoff. It asked if I wanted to restore a recent backup or upload one myself, I uploaded the backup I downloaded in step 2. It said I needed to change the IEEE address and that this was a permanent change, I said yes. Everything is working. No reboot of HA… Just worked! Thank you to all the people who made this function work! I’ve wanted to replace this stick with a newer one for years now!

Source: https://community.home-assistant.io/t/zigbee-stick-migration-just-a-little-help-has-anyone-used-migrate-radio-yet/472003