Is it possible to make integration with the ATOL 30F cash register

If the cash register does not have Ethernet and it is not accessible in any way outside (on the Internet), then it will be hard.
And in general, the problem is not a pleasant one.
Yes, the ATOL website says that there is WiFi, but this is an option.
Judging by the photo of the device, it does not even have Ethernet, but only USB 2.0. Therefore, it can only be connected to a computer.
In general, it is better to proceed from what the client needs it for and at what moment.
If the client wants to automate the cashier's workplace using OneBox, then it's better not to.
If a client has an online store, and at some stage of the sales process he needs to make a fiscal or non-fiscal check for the client, then this is another matter, this is real.