How should I do it?
Please let me know.
Please add documentation of hosting on Linode.
But I can tell you that the Ubuntu upgrade on Linode doesn't work well - they say so too - and I'm thinking of migrating to Debian (if that helps).
the Ubuntu upgrade on Linode doesn't work well
I can't imagine it would... OS upgrades usually are a little suspect, it's usually easier to just start fresh and migrate NodeBB back onto it, although I definitely get why an OS upgrade would be preferable in some setups.