Hi, I had all 0s for column C like you, and filed maybe a week or two ago with $1 in column C subsidy like you mention. It was the only way to make the form calculate that I could find and didn't know what else to do. My return was accepted. I've done it similarly in prior years (with no advance subsidy amount to report) so I don't expect issues, but it's only been a few weeks since I filed. I don't know why turbotax changed how it it worked this year.
I also don't like to take subsidy up front because I don't know what income will be.
