From the posts I found in a search, I should be able to upgrade from 3.30 to 5.4 without issue as long as the license is appropriate.
Has anyone done a single step upgrade? If so, what issues did you have?
Or, has everyone done a 4.x (4.17?) then 5.4 upgrade?

I've updated some Routerboards (Soho Router) from 3.30 to 5.4 - no problems at all (just upgraded licencing).

Regards