Installed rythm template into J4 and site returns Call to undefined method Joomla\CMS\Application\AdministratorApplication::isAdmin()

Hello there,

I hope you have had a backup of your full site. I am sorry to say but the templates are not compatible with Joomla 4 yet. Our dev-team is working on the compatibility and those will be compatible soon.

Till then, please restore the backup so that your site is fully workable.

Thanks!