Buuuut, D&D ain't exactly designed for solo stuff so I'm not sure if "Can this class function solo" is the best thing given I'm not sure all base classes would survive if we turned that lens on them
They all would survive, except like I said Bard, but the subclasses give even Bard an out.
5E is unique compared to other versions in that classes don't have a defined, locked in role. Some are inherently better than others at certain things but other than healing (which is uneccessary in 5E) every class can fill every role with the right build choices and generally do a good job at it.