[pests]

If they had time to prepare I'm sure they could develop a flow to get you a passkey on the new domain first. Similar to how YouTube used to do a bunch of cross-domain redirects (to plant cookies) to get Google+ login support back in the day.

[neurostimulant]

You might not get a head up when you're forced to change your domain though. For example, recently a huge number of .ml domains are dead and people that used them must scramble to migrate to another domain. The problem is some apps like mastodon (and now passkey) don't support changing domains unless the old domain is still accessible.