Netgear M1 external antenna compatibility?

I'm looking at picking up a Netgear M1 (4G/LTE battery powered cellular modem + router).

I'm going to be using it in the US for a couple of weeks this summer in a semi-remote area. I plan to use T-Mobile data (with AT&T as a backup if the reception isn't good).

I see that the device has two TS-9 connections for an external antenna and that Netgear sell the MR1100 as a compatible add-on.

I was wondering if there are other perhaps larger antennae that might be compatible .... or should any antenna that terminates in TS-9 and which covers the bands supported work in theory?