Replace your strap
The watch adapters seat in your mechanical watch's lug holes in place of the spring bars. Classic, Shadow or Titanium. The spring bar tool is in the box.
Living in two ecosystems is more common than people admit. An iPhone on one side, an Android phone on the other, and a watch for each.
Some test both, some are mid-switch. Smartlet keeps both on the same wrist on one strap instead of rotating two bands.
The watch adapters seat in your mechanical watch's lug holes in place of the spring bars. Classic, Shadow or Titanium. The spring bar tool is in the box.

Your smartwatch attaches to the central part of the bracelet with its own adapter (Apple Watch, Whoop, Fitbit, Galaxy or Pixel Watch) or a pair of standard watch adapters. Zero modification to the mechanical watch.
Both watches sit on the same wrist. The smartwatch sits underneath, against the skin; readings taken there are not certified by its manufacturer.