This is why I would never invest too much into Smart Home. While my phone may be expected to last for a few years only, I don't want my house deprecated because of a takeover/bankruptcy of a company.
Reconsider. I'd say these are two safe options: 1) Go with a cloud service using products exclusively made by a single major company, like Google or Amazon. This is simpler to setup and maintain but more expensive. 2) Go with an open source solution, like Home Assistant. Cheaper option with more control but requires a lot of time to learn, setup and maintain. Both options should be considered safe at this point. Edit…
3) Find a local home automation company and look at their offerings. There's a chance you'll find people willing to sell you actual products that are optionally Internet-connected, but not Internet-first, and are not tied to a garbage SaaS. They'll install and service them for you too. Key words here are "home automation"; I find looking for this phrase instead of "IoT" to weed out a lot of garbage.