Somebody has to pay for the support. There is no free meal.

Enterprise must be able to pay for support for as long as they use devices. Solved.

I can only think of requiring the devices to be serviceable, as you say. The absolute only way I can think of charging the consumers, ie the owners, is to charge a tax on internet connections. Then the government would pay somehow vulnerability hunters working along patchers, who can oversee each other.

Consumers are tricky: if you include support in the sale price, the company will grab the money and run in 3 or 5 years; and some companies will sell cheaper because they know they won't provide support.