Agreed, needing 6 probe ports will limit your choices. I've been researching the FireBoard Labs temp/control unit and it looks pretty cool. 6 probe ability, cloud connected, variable speed fan control if you plan on using a stoker and a nice app that keeps tabs on your cooks with temp and fan speed data with history. Also, it appears that FireBoard is a US company in Kansas City, MO and have started manufacturing their own printed circuit boards here in the US. I'd salute that move and support them going forward. Will probably be my next thermometer purchase when it's time.
https://www.fireboard.com/about/Another option is much cheaper, has 6 probe ability and connects to your smartphone via bluetooth.... It's the InkBird IBT-6x which can be had for around $50. I actually have this one and have used it once. It's ok if all you need is live data and you're going to be around the house within bluetooth range. No stoker fan control option for this one, but again it's budget friendly. Appears to be a Chinese company and the product support is lacking.
https://www.ink-bird.com/products-bluetooth-thermometer-ibt6xs.htmlThe unit I've used the most is my Maverick XR-50 which is a 4 probe unit, no app, but it comes with two units - one by the grill with full functionality and display and one remote unit which shows all 4 probe's stats and will alarm when temps are out of your set parameters. I like this unit because I can carry around the remote and get an instant update with a glance.....
https://www.maverickthermometers.com/product/xr-50/Many folk here and elsewhere like a unit called "Smoke". I have no experience with that one but seems to be present in a lot of videos I've seen.
Best of luck and hope this helps!