Sylvania Smart+ ZigBee Full Color Indoor/Outdoor Flexible Lightstrip - $16 on Amazon

In smartlighting choose turn on & set color, then you can choose color and brightness.

in a scene, when i tap ‘add device options’, which is where i normally set brightness, is just says ‘no more device options available’

check at https://account.smartthings.com what the Type field is set to for that device

ZigBee RGBW Bulb