In Android's Garmin Connect app v4.19.1 there is an underscore pretended to the Min Respiration Rate. To view this:
1) select an activity (I've only done a run so I cannot confirm nor deny other activities are the same) where an external HRM was worn
2) Select the list looking icon to see a list of stats for that activity.
3) Scroll down to the Respiration Rate section.
If this is not the place for bug reports, please let me know where the appropriate forum is.
Cheers