In his 1911 volume Fruit Farming for Profit, Mr George Bunyard recommends a few different half-acre orchard planting schemes, each of which is adapted to suit the purpose of the plot. Here’s his suggestion for a “typical home orchard, for the supply of a family”:

“HOME PLANTATION. – Standard Apples or Plums 18ft., with Bushes,
or Raspberries and Strawberries between.
132 Standard Trees and about 200 Gooseberries, 2000 Strawberries, and 500 Raspberries per acre.“
Damn. Either our Mr Bunyard had a very big family, or they managed to get through a lot of jam.
Joking aside, it does demonstrate that when you’re not constrained by the need to provide access for machinery, and are growing trees as traditional standards rather than in commercial cordon, spindle etc. systems then there’s plenty of potential within an orchard space for inter-planting with lower-growing fruit crops.
These friendly plant-neighbours will provide ground cover (keeping weeds down), additional nectar for pollinators (attracting more of them to the orchard and keeping them coming back to the plot throughout the year), habitat for predatory insectivores (small birds as well as other insect species), and lots and lots of lovely fresh fruit… and jam. (So much jam.)