I have a droplet running a LAMP stack that is getting a bit out of date (running Ubuntu 16.04). I want to move the whole thing to more recent versions of everything (Ubuntu 18.04, and application software).

I don’t expect this to be near instantaneous, so I intend to add another droplet, install the recent software on it, and script the data import from the older droplet and test. Once everything works, I’ll do a last data import and open the new droplet to the public.

Now, the site has a name so people access it with DNS resolution. If I change the DNS record it will take over 24Hours to percolate to users. DO offers a “floating IP” that could make the switchover a lot faster, but it says “Floating IPs do not support PTR (rDNS) records.” and I don’t know how important that is (for instance for an anti-spam filter when the server sends mail to users).

The site use HTTPS with a certificate delivered by LetsEncrypt. Can I carry over the certificate (after all it will be the same CN and SAN) or do I have to request a new one?