Hello,
Thank you for reaching out.
First of all, it is important to mention and keep in mind that the RUT271 is a RedCap 5G router that supports only the 5G Standalone (SA) architecture. This means it will only connect to 5G (SA) networks if your mobile carrier has deployed the required infrastructure. If not, the modem will fall back to LTE/4G only, as discussed in the thread here:
Considering your traveling use case, if a reliable 5G connection is essential for you, I would recommend looking into the following alternative routers:
Regarding external antennas, once the router choice is confirmed, I can recommend the best fitting, optimal performance antenna type/model for your use case.
Best regards,