We can change the shape of the app icons or symbols in the OnePlus smartphone's home screen settings to further customize the overall design to the user's needs.
In addition to the pre-installed Oxygen or Hydrogen Icon Packs, other icon packs can be downloaded by clicking on the pre-defined button. This allows us to specify numerous designs of app icons, which can be square, fully round or rounded, to name a few examples.

Android 10 | OxygenOS 10.0
Step 1:  Tap and hold a  free area  on home screen
Step 2:  Tap on  Home settings
Step 3:  Tap on  Icon pack
Step 4:  Choose an  I  con pack
Step 5:  Tap on  Save
  1. Tap and hold a free area on home screen
  2. Tap on Home settings
  3. Tap on Icon pack
  4. Choose an Icon pack
  5. Tap on Save

OnePlus Instructions