How to change listing per page option?

Go to admin Store > Configuration > Catalog > Storefront

Now there are two things

• Products per Page on Grid Allowed Values

  Enter your desired no here with comma like 12,24,48,96

• Products per Page on Grid Default Value

  Value you enter here must be defined in Allowed Values.

  like you can enter from these values only 12,24,48,96.

See how it looks after changing

Clear your cache and it should work smoothly

you can change in admin Store >> Configuration >> Catalog >> Catalog >> Frontend TAB

You can change it via admin panel in section Stores -> Configuration -> Catalog -> Catalog.

You are interested in the fields Products per Page on Grid Allowed Values and Products per Page on List Allowed Values.