Thanks for the education on NVM vs n. I understood this much differently.
The hoops/steps to change Node version are significant. I am thinking it would be better or at least a bit easier to deploy new server that is already using the desired Node version then migrating the Ghost site to new server.
Yes, 16 is working fine but 18.xx is current supported version. Whether one upgrades Node now or later eventually it would be less of an optional thing. Upgrading is a certainty at some point. May as well learn the in and outs of doing so now.
FYI: I think Ghost folks have updated DigitalOcean one-click but the old version is still being deployed as of a couple of days ago.
BTW: Difficulty udpgrading Node is what lead to Installation Errors Using Official Doc