Used this for the first time today after having to buy a last minute UA ticket thanks to AA.

Added it straight onto the reservation when I purchased the ticket. The *G showed up on both the mobile boarding pass AND the physical printed one.

However at the EWR UC they tried to deny me twice (left for Starbucks and came back with different agents at the desk upon return) saying I wasn't eligible until I pushed them on it being *G on a non-US (read not UA) carrier. Both times they ultimately relented and said they would just manually enter it and I'd be fine.

So I'm pleased since it's clear it works for UC domestic access but I'm not pleased that it wasn't automatic despite being listed on the BP.

I didn't bother trying to change the FFP since it's a short flight so not giving up too much mileage wise and I didn't want to bother with the hassle. Next time I'll just attempt to leave my SQ or UA number on the ticket and bring the printed out card and see if I can get in with that.