Can anyone confirm if ZTE 4G Dongle - MF833U1 works in old style serial usb mode? Or other suggestion for that functionality

This is one of the only usb dongles I can find to buy new here in the UK.

2nd hand there are lots of different ones but I am paranoid of a 2nd hand one containing some malware.

The D-link dwm-222 was no go as that uses RNDIS on new firmware and was unable to downgrade to previous where it didn't it so sent back for refund.

E3372h-365 is available however looking online it seems like a convoluted route to downgrade firmware for that too. These have the advantage of being widely available and perhaps would try this as a last option if cannot find another one which would be more straight forward.

So how is the ZTE 4G Dongle - MF833U1 out of the box? I just want a serialusb modem to show up in /dev/ttyUSB* to enable me to use sms commands in ModemManager. Note I already have a 3g huawei but I want a 4g one as 3g has been shutdown in the UK now, leaving only 2g speed for internet access, which I also want to use it for.

So can anyone confirm what the ZTE 4G Dongle - MF833U1 will show up as? Is it another one of these annoying ethernet links or is it the classic tty serial modem? I have not been able to find any information for this specific model online so far pertaining to this specific query; only other zte models.

Alternatively any other one you could recommend which would however I doubt I could find it on the UK market anyway as what I listed is all I could find which may suit the job and are still available. I definitely want dongle only not any mifi or such since I want to use on laptop without any mains access and simply for the superior portability of the little thumb drive dongles.

EDIT: Arrrgh! Saw this comment on amazon reviews for the product:

I was looking for a USB 4g/5g dongle to attach to my ASUS router so that it can automatically switch to it if the main fibre broadband goes down as I generally work from home. This dongle seemed very reasonable (despite being "only" 4g) and it uses "usb ethernet" to provide the actual connection via an in built router.

This is also what the posts on the forum say, if you look for "MF833U1".

I had already done a search, I must have missed it, had many browsers open doing many research queries yesterday.

Conversely then do you know of any that WILL give ttyUSB out the box (or with simple mode switch) on linux. Again, dongle not anything else.