Modem showing up at /dev/ttyS2 instead of /dev/ttyUSB1 and factorytest times out

[Subsentient]

I would advise you to contact Quectel and ask them for a copy of the firmware for the EG25-G, along with the latest update tools for Linux. They do have a special application you can compile on AArch64 to flash the modem. I flashed mine. I'd post the firmware here, but it seems they don't want you to do that. Their license for some of it is actually illegal, so it muddies the water. One of the tools, I forget which, claims "Public domain -- for Quectel customers, nobody else is allowed" or something like that. You'll have to ask Quectel directly. They also have a good, knowledgeable tech support team, they may be able to help.

I can't promise it will be possible to flash the modem over serial, but it's worth a try.

EDIT: If you PM me, I can send you the email of the technician that was most helpful to me.