@gorkemh Looks like we have found the conflict! Could I please ask what theme it is that is causing the issue? You could try contacting the theme makers and letting them know of this or as you suggest you could also use a different theme but that decision is entirely yours.
@gorkemh You are very welcome and glad I could help you with this!
We can only provide support for the Site Kit plugin here so unfortunately I can’t suggest a new theme for your site but I am sure you will find a suitable one to go with.
Is there anything else on the Site Kit side of things that I can help you with?
Version 1.137.0 of the Site Kit plugin has been released, and I’ve applied the update. After that, the 500 error on the homepage was resolved. Just wanted to inform you.