https://forums.garmin.com/apps-software/mobile-apps-web/f/garmin-connect-web/54269/measurement-units
Per this 13yr old post, I'd request that Garmin Connect Web and Garmin Connect App, please consider implementing user configurable custom units of measure for every recorded metric type.
This is implemented correctly on my FR965, unit types for weight/height/distance can all be selected
So as you can see, this is not breaking new ground.
I'd like to see Garmin support seriously consider examining this request, send it up the chain to acquire a resource and follow through. This is low hanging fruit given the code is already written and owned by Garmin - it just has to be ported from one platform to another. This would help to bring Garmin connect more in line with industry standard health tracking applications which already have this standard user Ux feature.