After updating to 5.9, when the posts page is loaded in the browser it uses wp-includes/template-canvas.php?

this happens because wp_enable_block_templates() is enabled.
Try to navigate to wp-includes/theme-templates.php and comment that function, its placed at the end of the file.

Let me know if it worked, good luck!

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)