What are the open problems concerning *all* the finite groups?

The references will be appreciated. Here are two examples:

**Aschbacher-Guralnick conjecture**(AG1984 p.447): the number of conjugacy classes of maximal subgroups of a finite group is at most its class number (i.e. the number of conjugacy classes of elements, or the number of irreducible complex representations up to equiv.).**K.S. Brown's problem**(B2000 Q.4; SW2016 p.760): Let $G$ be a finite group, $\mu$ be the Möbius function of its subgroup lattice $L(G)$. Then the sum $\sum_{H \in L(G)}\mu(H,G)|G:H|$ is nonzero.

There are two types of problems, those involving an upper/lower bound (like Aschbacher-Guralnick conjecture) and those "exact", involving no bound (like K.S. Brown's problem). I guess the first type is much more abundant than the second, so for the first type, please restrict to the main problems.