Linux that works without constant under-the-hood tweaking (ala early Windows flavors, 3.1, 95/98). Does such an OS exist? For the record, I am not an IT tech. I just need something to work with the mechanical equipment it controls. Any recommendations?
In short, there isn't one and will never be one.
Linux distributions are based on the assumption that there will always be someone, somewhere, who can interpret the misleading, technically dense, and often incomprehensible data, conditions and messages that Linux: both the O/S and the applications it runs, constantly throws at its users.
The best possibility is to find a version of Linux that does what you want it to, install it, then keep it far away from any and all internet connections. That is the only hope you have that it won't try to update itself, install new versions or discover that external stuff it expected to find has mysteriously been moved or deleted by the notional owner.