You don't have to run it a entire duplicate of your current infrastructure, just plan for it to happen (depending on impact to your business). Then it means you can think about doing it after a few days of downtime, maybe earlier depending on difficulty/impact.

But, yes, you do have to plan to run it elsewhere and consider wether various features may make it harder for you to move on. vendor lock-in is a known business risk

Running multicloud (at the same time) is for availability not disaster recovery. Just having another copy of the data outside is good for DR, even if you have to redeploy everything manually in a hurry.