Whenever I contemplate putting an ancient device (back) on the air, I always end up finding out, that at least one of the wireless technologies/chips aboard the device has security problems, and replacement firmware (if the problem is fixable by SW/FW) is usually not available, or from dodgy sources with unknown "goodies" added. (In those cases, I also don't trust the soft-toggle in the UI)

PostmarketOS is my current "Favorite" FW for hopefully getting some old devices back into service, mostly for interfacing with some IOT installations. They are working to get the Mainline kernel to run on many old(er) devices, since these days only a correct DTB is required to boot on nearly anything. (iiuec)