Hello Antoni,
The TTGO can operate at 868Mhz, which is what I believe is the correct frequency for the EU, but someone who knows more can correct me.
If you order the exact link I provided, the board should arrive pre-flashed with the disaster radio firmware, though it will be an old version, so it may be best for you to learn to flash them yourself, especially if you plan on deploying a lot of them.
Also, you gave me an idea to allow configuration of the LoRa frequency through the console or web gui. I'm going to open an issue for this right now,
Thanks and let me know if there are any other question we can answer,
-grant