If moving from one LTS version of the OS to the next version, I’d expect a fairly smooth process. So, I might take a backup - of course - and download it for safety - of course - and then try the OS update. If it didn’t work, I could then try a fresh OS.
But in doing this I would take more forum downtime.
I’m a little reluctant to migrate to a fresh instance mainly because I’d need to update the DNS and wait for it to propagate. Although I see the post above me says I could take my IP address with me, which is nice, and which takes this reluctance away.
In fact, changing my answer entirely, if I can take my IP address to a new instance that would be preferred. Possibly not all providers allow this. Possibly for some providers one would lose a no-cost IP and start paying for the IP, because it has moved even though it hasn’t changed.