What I've found that works (for me):

For stuff that isn't yet rusted, Fluid Film. It's easy to buy (it's on the shelf even at Wal-Mart). It's made primarily from lanolin, which is a product of the wool industry and is how sheep stay dry. If I were Very Serious about it, I'd find a shop that would cover the whole bottom of the vehicle (and anything that can be reached through holes) in the stuff and pay them to get that done. (I buy it in spray cans; some shops buy it in 55 gallon drums.)

For stuff that is definitely already rusting, Corrosion-X. It's some kind of oily chemical soup that is supposed to prevent existing rust from getting worse, and also prevent new rust. One interesting feature is that it's available in 3 different viscosities; vaguely speaking, those viscosities are thin, medium, and elephant snot.

The thin one does a fantastic job of creeping around to cover even unseen surfaces, but it washes off the fastest. The thicker ones hang around longer and creep less. (Tradeoffs, I guess.)

I prefer Fluid Film just because it's more natural than some other things are and that makes me feel good in some way that I don't care to rationalize, but Fluid Film is not very good at recovering from existing rust.

Corrosion-X, though? I can get the thin version of that worked into the joint of a completely rusted-stuck pair of box-jointed pliers and have them working very well (and looking fairly decent, though not "new") in a few minutes with a shop rag. I've heard stories of it being used to hose down whole electrical rooms in ocean-going boats. It's amazing stuff. (And it's expensive.)

The practical downside is that these products all feel greasy, and they all turn black with enough time and enough miles. They're all ugly.

For visible painted body panels, the best way I know to deal with small spots of rust from rock chips and stuff is to go full-ass on it. Get the Dremel out, pick an appropriate abrasive stone, and start grinding those little pinholes out until there's nothing but clean, shiny metal surrounded by paint. And then: Fill in with touchup paint that matches the factory paint code. (It's never perfect, but it does get easier to do a job that looks better than little rust spots do with some practice...and the little spots then don't turn into big spots.)

Rust never sleeps. Good luck.

Why don't classic manufacturers not ramp up their software quality side? I mean it's 2025, they lag behind at least a decade, but software development (infotaiment) practices seems like dark ages.

Except for MCU - from user perspective they just work.