[iv597]

3138 used 4G tablets standalone last year at Queen City and Championship.
4G USB adapter -> router -> ethernet switch -> USB ethernet adapter -> OTG cable -> tablet at Crossroads and IRI (trust me, it's as bad as it sounds). Even though ethernet wiring was a complete PITA, it was quite reliable, and broke no rules. Though do yourself a favor and go with an OTG adapter that has both a power plug and an ethernet adapter, and not a generic OTG->USB-A adapter.

4G radios on their own is of course optimal if that's an investment your team can make - it's just not always working well at venues (see: Crossroads).

BT PAN was flaky when we tested it, but we're looking into it again this year. Who knows.

Just my $0.02, given IPA gave us quite the crash course in this type of thing last season.