AMP 1.5.2 completely breaks site

Hello,

AMP 1.5.2 completely breaks my site:

Notice: is_amp_endpoint was called incorrectly. is_amp_endpoint() was called before the wp action which means it will not have access to the queried object to determine if it is an AMP response, thus neither the amp_skip_post filter nor the AMP enabled publish metabox toggle will be considered. Please see Debugging in WordPress for more information. (This message was added in version 1.0.2.) in /var/www/html/wp-includes/functions.php on line 5167

This blog is running a plain vanilla version of TwentyNineteen via a child theme that makes very few changes (simply because I’m incapable of learning CSS no matter how hard I try).

AMP was fine until 1.5.2.

Can someone help me figure out what changed and maybe offer a clue of how to fix it? The plug-in is (temporarily) deactivated.

Thanks.

The page I need help with: [log in to see the link]