UPDATE - I THINK I SOLVED THIS MYSELF and putting it out here for the group to see.
(1) It appears that the “autoselect” MBB in the modem picked COMMERCIAL-Tmobile, which would be normally ok. BUT I seemed to remember something about selecting a generic profile in the modem.
I listed the profiles here:
AT+QMBNCFG="list"
And found a “generic looking” profile as:
"ROW_Commercial",0xA010809,202306011
(2) Used the following AT command strings.
Turned off auto select and deactivate with
AT+QMBNCFG="AutoSel",0
And then entered:
AT+QMBNCFG="Deactivate"
Then selected the proper “generic” modem
AT+QMBNCFG="Select", "ROW_Generic_3GPP_PTCRB_GCF"
Checked to be sure the profile is selected:
AT+QMBNCFG="list"
And saw the 0,1,0 was in front of the profile at the top of the list (above TMO)
+QMBNCFG: "List",0,1,1,"ROW_Commercial",0xA010809,202306011
+QMBNCFG: "List",1,0,0,"Commercial-TMO",0xA01050F,202303091
Then REBOOTED.
I made sure the APN was fbb.home and all connected well and things are working perfectly
FOR RESEARCH SAKE, I set the system to AUTOSELECT again with
AT+QMBNCFG="AutoSel",1
It went back to TMO and fbb.home did NOT work properly.
So - in this case, to make sure that the PROPER APN fbb.home is working for a TMHI sim in this unit, this procedure here seems to make this work correctly!