[berkes]

In practice, updates might be possible, but you'll often see hardware stopping working.

If it is "just" bluetooth, that may be fine. When networking (wifi/GSM) or the screen stops working, it probably is not.

I've done a fair bit of upgrades of ancient android phones to CyanogenMod, LineageOs and even an accidental Ubuntu Touch. Fairly common that things like the camera or bluetooth stop working (partly), but for many owners of old phones, that is certainly a trade to make. "I never use Bluetooth, what could you use it for?", "Oh, but then I'll just use this jack-cable for my sonos").

What I'm trying to say: yes: updates require SoC vendors to help, or at least stay out of the way. But no, that does not mean one cannot ever update at all.