@J F Ogilvie
Take a look at what's new in Differential Equations in Maple 2021 page. That page answers - not a generic question on "number of solutions" (there are infinitely many possible ODE problems) - but what I meant by skyrocketed (informal for increase very steeply or rapidly).
In brief, the problem of 2nd order linear ODEs splits into those that admit Liovillian solutions and those that do not. In the second set, the approach is to compute hypergeometric or Heun function solutions; the corresponding standard and some original approaches were implemented in previous Maple releases.
In Maple 2021, however, we implemented something far beyond that. For example, as said on that what's new in DEs page, none of the ODE problems shown there can be solved in Maple 2020 or before, or using other computer algebra systems. At the end of the ODE section of that what's new page, you will also see seven references to the scientific literature explaining the new methods and how they extend previously existing ones.
So while It is true that the Maple ODE and PDE solvers were already state-of-the-art in previous Maple releases, in Maple 2021, regarding 2nd order linear ODEs and ODE / PDE problems that require solving that kind of problem as an intermediate step, the solving capabilities skyrocketed. This achievement is a milestone in computer algebra and differential equations.
Edgardo S. Cheb-Terrab
Physics, Differential Equations and Mathematical Functions, Maplesoft