It was an unnumbered exit, then it was Exit 0 to Riverfront for a brief time, then as part as the rebuild the exit point was moved to 40th Street instead of 41st (which it was as recently as December 2021).
Needless to say, but I'll say it anyway, that I'm happy we have an Exit 0, but I'm less happy that the I-29 exits appear to be left completely unnumbered instead of 0B-C or 1A-B.