Are staff in public institutions allowed to work part-time outside?

The staff of public institutions are definitely not allowed to work part-time outside, but this is not allowed, because the unit knows that you have another job outside, so it will not be allowed. But if you are a creator, for example, you can use your spare time to create online, whether it is literature or other aspects, these are your legitimate income. This kind of work is allowed as long as it does not affect the normal work unit, but what the unit explicitly prohibits is that you have another job outside, get another salary, and even have to go to work where another job goes to work. This situation is absolutely forbidden. Because institutions also belong to a class of big civil servants within the scope of state establishment.