OK, followed instructions to reset the Bluetooth module (in Ventura), and then as per instructions shut down (process obviously does not notify success or failure).
Next, I was not sure whether the reset SMC required a restart after shutting down, so first attempted to do so while shut down. Pressing the specified keys merely started up, so retried after startup was complete and followed the steps, which ended in a black screen, so, assuming all well, started up as instructed ( - again no notification of success or failure, but I presumed success).
Next opened bluetooth settings to re-pair my earbuds. They were still there in the list of devices, so no need to re-pair (does this mean the reset of the bluetooth module had failed?). Clicked connect and the same thing happened: they connected, sound stayed coming out of the built-in speakers instead of outputting through the buds, and the connection then dropped out after about ten seconds.