SOLVED!
I’ll keep this topic rather than delete it just in case somebody else has similar issue, but I figured it out. In short, I had a space on the end of my NwkKey.
The combination that first got the node conencted was using the RadioBoards.h library AND checkiny all of my keys (I should have done this sooner). They were all ‘correct’, but I found a space on the end of my NwkKey and once delected, the board was able to connect to TTN and I was able to see the device all the way through to my Home Assistant instance.
I confirmed that manually entering the LoRa pins as (18, 26, 14, 33) still returned the invalid frequency error and that entering them as (18, 26, 23, 33) returns the same.
It appears that the config.h file has some ideas about other ‘manual’ pin settings to try, but I’m not sure it’s worth it since the automatic setup with RadioBoards.h worked, but here is the section of that config.h file that give those suggestions anyway:
// LilyGo
#elif defined(ARDUINO_TTGO_LORA32_V1)
#pragma message ("Using TTGO LoRa32 v1 - no Display")
SX1276 radio = new Module(18, 26, 14, 33);
#elif defined(ARDUINO_TTGO_LORA32_V2)
#pragma message ("Using TTGO LoRa32 v2 + Display")
SX1276 radio = new Module(18, 26, 12, RADIOLIB_NC);
#elif defined(ARDUINO_TTGO_LoRa32_v21new) // T3_V1.6.1
#pragma message ("Using TTGO LoRa32 v2.1 marked T3_V1.6.1 + Display")
SX1276 radio = new Module(18, 26, 14, 33);
#elif defined(ARDUINO_TBEAM_USE_RADIO_SX1262)
#pragma error ("ARDUINO_TBEAM_USE_RADIO_SX1262 awaiting pin map")
#elif defined(ARDUINO_TBEAM_USE_RADIO_SX1276)
#pragma message ("Using TTGO T-Beam")
SX1276 radio = new Module(18, 26, 23, 33);
