Lightburn desconectado del laser indica “ready” (LightBurn disconnected from laser indicates “ready”)

"What will be the reason why it is necessary to switch to another COM port now, when this was not needed before?
"
This is one of the nuances of USB devices. The devices are assigned to COM (communication) ports dynamically and a device can have the same number for a long time, then change when something else is plugged in for a while.

"Is it necessary to install the CH340 driver anyway?"

I do not believe so. If the Driver was not present, it’s very likely that the communication would be distorted or missing. If the communication begins to show problems, using the most recent driver from the chipset manufacturer may be a good first step… next time.