One time purchase + annual maintenance fee is a pretty common pricing model.

If the product stops working if you don’t pay the maintenance fee then it’s a subscription model with an initial down-payment. Car maintenance doesn’t fall into the annual fee model, as much as manufacturers and dealers would like, you don’t have to use them for periodic repairs or servicing. Car features that require yearly renewals (navigation and the like) would be subscriptions with a one-time free trial.

One time purchase plus yearly renewals to keep the product operating are one shaky legal grounds.

I think you're misunderstanding the above comment. Buying a perpetual license for a particular version (or set of versions), then in the future optionally paying a fee for a new major version not covered by that license is extremely common and imo the most fair model for both creator and customer. If you never buy an upgrade or newer version, the version you own continues to work the same way it always has. You just don't get the newest updates for free.

It's common and fair, but it seemed it somehow didn't qualify as outright ownership.

My car comes with free recall servicing (security updates) and a manufacturer warranty.

I bet this doesn't come from the kindness of car manufacturers, but through laws and regulations requiring that.

We probably don't have any of that with software, yet.

Some jurisdictions do.

Security updates is not a new model; most cars come with a warranty (which is not the same thing either but the point is you do get some form of support for free for a period of time).