It is never allowed to fly over assemblies of people, however a C0 drone may be flown over uninvolved people if it cannot be avoided.

Suitable C-classes	C0 or no C-class<250g
Subcategory	A1<250g
Maximum altitude	120m AGL or less
Flying over uninvolved people	C0 - should be avoided when possible

Implementing regulation (EU) 2019/947
AMC1 UAS.OPEN.020(1) and (2) UAS operations in subcategory A1

(b) It is accepted that UAS in class C0 or privately built UAS with MTOMs less than 250 g may fly over uninvolved people; however, this should be avoided whenever possible, and where it is unavoidable, extreme caution should be used.

Definition of uninvolved persons:
Persons who are not participating in the UAS operation or who are not aware of the instructions and safety precautions given by the UAS operator.

You can find a complete definition in Cover Regulation to (EU) 2019/947, GM1 Article 2(18) Definitions.