Is there a usable Linux driver for the MT7902 yet?

You may not be doing anything wrong. Reports about a driver being planned or patches being submitted do not necessarily mean the support is ready in a released kernel. The discussion here suggests the work has not yet reached a reliable, generally available state, so a newer version number alone may not help.

For troubleshooting, include your distribution, exact kernel version, the computer or motherboard model, and what the system reports for the device. Those details can distinguish a missing driver from a driver that loads but fails, and they make it easier to check whether a particular distribution has backported anything.

If you need working Wi-Fi now, using a known-supported adapter is the practical workaround. An older card that already works is a reasonable temporary option. I would avoid relying on unofficial driver builds unless you are comfortable checking their status and rebuilding or fixing them after kernel updates.