I have a six year old iMac running OS 10.10.5. This is the latest OS I can run on my iMac. But your ICC application for Mac needs 10.13 or later to run.
Is there an older version of the ICC APP that I can run on my iMac?
I believe Lantern will work http://www.lanternchess.com. Lantern is now listed on the icc download page. I dont have that OS but it ran in past when i had it and dont believe much has changed. Give it a try and let me know.