Hi @punkie The latest Samsung watches (Galaxy 4 and 5) are compatible with any Android device as long as it is running Android 8 and above with at least 1.5 GB of RAM. However some limitations in the Health functions if you do not have a Samsung phone (such as ECG and Stress ) see more here : https://www.cnet.com/tech/mobile/samsung-galaxy-watch-5-everything-new-from-better-battery-to-skin-t...
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 4.0,Android 12 Official Version.