OP, do you think it is worth helping your dc deal with the emotions arising from the bullying and their feelings about what has gone wrong with activities in the past, and building up confidence, before finding new activities to try? Also to find out what would really tick your child's boxes if they had all the confidence in your world, and slowly help your child in that direction?
Trying a new activity presents a whole new set of rules to learn and people to meet, which could create new anxieties?
Out of school activities are sometimes harder for children who have experienced trauma (if this applies to your ac?) because they are often less structured than school, the children behave differently, and this can be stressful for a child who is more easily knocked off their feet than the average.
If your child enjoys sports but finds the clubs hard at the moment, for example, you could say help the child improve their fitness and practice skills so that they can they fit in again more easily when they are ready. Once someone has sporting skills in any direction they find it easier to pick up new sports, just picking up on sander's point.
Another benefit of running as a way of building up general fitness, incidentally, is that it helps with emotional regulation, feel good hormones, confidence.
It depends on your child obviously, and their interests, and the reasons why they are wanting to back off.