It depends on what you think is straight forward, do this for every region (1-151)
https://vapi.splinterlands.com/land/deeds?status=map&region_number=1

Then get the player from the deeds section and count 😁.

If you are using python

• put the [data][deed] from every call in a dataframe (pandas)
• concat all the df together
• df.player.count()

something like that.