Hjack dont be put off. I will answer your question as I learned to ride as an older adult and had the same problem.
In the UK the general rule (BHS) is that a person must be able to canter in the school before they are allowed to hack.
There is a reason for this. If a horse gets frightened and spooks, it may canter off and if a learner cant yet canter they may fall off.
I was allowed to start hacking after my lesson horse spooked and cantered in the school (I was trotting over poles) and I didnt fall off. However, I went on having lessons and I didnt canter on hacks for some time. I didnt fall off but I would not say I was competent or confident in canter.
However, if you are allowed to go out on a hack before you can canter, it is sometimes easier for beginners to learn to canter on hacks because there are no corners. It can be hard to balance in canter at corners in the school. There are some riding schools or trail ride centers which specialise in teaching canter out on hacks and that is how I learned to canter properly.
Some schools teaching canter out on hacks, teach one to use a forward or light seat. Mine did not, yet strangely, they always cantered up hills. Some RIs believe this makes it easier as the learner does not tip forwards. But it also means that the seat of the learner is deep in the saddle and if the horse has a bumpy canter, that makes it harder.
I always find it best to ask the advice of the RI about any particular horse. But I have been cantering for years and out of habit canter up hills even though the horse I ride at the moment has a very bumpy canter. So I need to re think things myself.