I read on the Hardwood Installer website that I need to glue the t-mold instead of screwing into concrete. However, it doesn't advise which substrate to glue to - either the wood floor or the ceramic tile.

I use silicone, not glue. Make sure its 100% silicone, not siliconized caulk. Never had a molding come loose yet.

Whatever you choose to use, squirt it in the groove/gap between the two floors.

Glue it to the concrete.

Thanks to AustinFloorguy & bayside. So I should use 100% silicone and glue it to the concrete.

That's what I use. Mainly because if for some reason you do need to pop it back out, it would be easier than if you used something like liquid nails. That, and it still holds like a son of a gun. Like I said, I've never had one come loose on me. Just make sure you use enough.

Be nice to have some pictures of that procedure. Even a video!