This script returns the domains and what percentage of your followers belong to them. Updated version at https://git.kokolor.es/imo/follower-stats

follower-domain-stats.lua

#!/usr/bin/env lua
-- This script returns the domains and what percentage of your followers belong to them.
-- Works with Pleroma and Mastodon
--
-- Usage:
--   lua follower-domain-stats.lua INSTANCE USER_ID [ACCESS_TOKEN]
--
-- Example:
--   lua follower-domain-stats.lua https://edolas.world 1 1234567abcdef
--
-- Note: ACCESS_TOKEN ist only need on Mastodon, on Pleroma you get the followers without it

local requests = require('requests')

local url = arg[1]
local id = arg[2]
local access_token = arg[3]

local function percentage(stats)
  local p_stats = {
    followers = {},
    following = {}
  }
  
  for tname, tbl in pairs(stats) do
    local total = stats[tname].total

    for dom, val in pairs(tbl) do
      if dom ~= 'total' then
	table.insert(p_stats[tname], { dom, ( val * 100) / total })
      end
    end

  table.sort(p_stats[tname], function(a, b) return a[2] > b[2] end)
  end

  return p_stats  
end

local function main(url, id, access_token)
  local stats = {
    followers = {
      total = 0
    },
    following = {
      total = 0
    }
  }
  local headers = {}
  
  if access_token then
    headers['Authorization'] = 'Bearer ' .. access_token
  end
    
  for tname in pairs(stats) do
    local resp, err = requests.get({ string.format('%s/api/v1/accounts/%d/%s', url, id, tname), headers = headers}).json()
    err = resp.error or err
    if not resp or resp.error then error('The following error occured: ' .. err) end
    
    for _, val in pairs(resp) do
      local domain = val.acct:match('^.*@(.*)$') or 'local'
      
      if stats[tname][domain] then
        stats[tname][domain] = stats[tname][domain] + 1
      else
        stats[tname][domain] = 1
      end
      stats[tname].total = stats[tname].total + 1
    end
  end
  
  return percentage(stats)
end

local stuff = main(url, id, access_token)

for n, t in pairs(stuff) do
  print(string.format('Percentage overview for %s:', n))
  for _, p in ipairs(t) do
    print(string.format('  %s: %.2f%%', p[1], p[2]))
  end
end

Updated version at https://git.kokolor.es/imo/follower-stats