Won't other probes work on the older MAK controllers? I took their e-mail as they are having a hard time finding a US Manufacturer of the barrel plug probes, but if you knew the specs, I'd guess someone else's probes would work just fine from Thermoworks, Fireboard, or generics from Amazon. I don't have experience with the old controller, but my understanding is that there's a lot to gain from upgrading to the new. I thought I heard that the older controllers will not run the latest firmware. The new controller and firmware have a lot of claimed improvements over the old. I only say claimed because I don't have any experience with the old to compare to. Type-K probes are universal. MAK's new probes appear to be great quality, but you should be able to use any type k probe with the new controller.
To the point of maintenance, that's always a risk with tech. Pellet grills move more and more tech all the time with WiFi, apps, probes, etc. The tech around them will become obsolete with time. New WiFi 6 standards and routers are coming out that use a new 6GHz band. I haven't studied it much yet, but I wonder if it's penetration will be better than 5GHz? If it is, 2.4GHz could start disappearing over the next few years. 2.4GHz is the only thing all the pellet grills I've seen support. When will support for old standards quit getting added to all routers (802.11 a/b/g/n)? As well, how long will companies support old grills in app updates? They have to update their apps frequently for OS updates, if they change things in the data formats over time (likely to improve things with newer models like more information or better tracking), they could have to maintain differences between several different grill models and grow tired of it over time and just start dropping app support for older grills.
As far as going to gas, Weber has new models out this year with an integrated Smart Connect hub and probes. So, they're likely on their way to become standard on most of their gassers over time. Moving to gas might not save you any headache. With the Masterbuilt and CharGriller Gravity Feeds drawing tons of attention, it sure looks like charcoal is heading to full on tech as well.
You old xxxxxx better run out and get your offsets, kettles, and WSM's now before they start moving them into the current times
It will be scary and funny when an old Traeger with the classic Smoke, Lo, High only settings are the most sought after pellet grills and start fetching tens of thousands on eBay.