How to end the Zoom-steals-focus-on-launch nightmare we've all been experiencing.

init.lua

-- You need Hammerspoon to run this: http://www.hammerspoon.org/

-- Zoom is a focus nightmare. This script will steal focus back from Zoom for zoomBlockTime seconds, at launch.
-- If you don't switch to another app Zoom will stay active.
-- If you activate (focus) Zoom from Finder, it'll accept your focus change.
-- If you focus, say, your chat app to tell someone you've launched your Zoom meeting, focus will switch back
--   to that app every time Zoom tries to steal it. Today, it's 5 times on my machine.

zoomBlockTime = 10
zoomFocusBlocked = false
foregroundAppName = nil

function zoomWatch(appName, eventType, appObject)

  -- watch for launch event and start a timer
  if (appName == "zoom.us" and eventType == hs.application.watcher.launched) then
    hs.alert("Zoom Launched. Focus theft blocked for " .. tostring(zoomBlockTime) .. " seconds.")
    zoomFocusBlocked = true
    hs.timer.doAfter(zoomBlockTime, function()
      zoomFocusBlocked = false
      hs.alert("Zoom focus unblocked.")
    end)
  end

  -- handle focus theft if zoom is launch-blocked, unless it's from Finder
  if (zoomFocusBlocked and foregroundAppName ~= nil and appName == "zoom.us" and eventType == hs.application.watcher.activated) then
    if (foregroundAppName == "Finder") then
      hs.alert("Zoom activated from Finder. Allowed.")
    else
      hs.alert("Zoom tried to activate from " .. foregroundAppName .. "; denied")
      -- reset activation
      hs.application.get(foregroundAppName):activate()
      print("Reset activation to " .. foregroundAppName)
    end
  elseif (appName ~= nil and appName ~= "zoom.us"  and eventType == hs.application.watcher.activated) then
    foregroundAppName = appName
    print("foregroundAppName set to " .. appName)
  end

end
zoomWatcher = hs.application.watcher.new(zoomWatch)
zoomWatcher:start()

Short screen cap demo.