Before the update to "Hogfather" I had the Blockquote Plug-in running. Also before updating I noticed that the Plug-in was not compatible with 2020-07-29 "Hogfather" so I deactivated it (and used a self defined WRAP-Block instead).
Now I noticed that the status switched to "Compatible with DokuWiki 2020-07-29 "Hogfather" yes", so I activated it in the admin pages. After that the webpage breaks and I get these messages in the apache log file:
[Wed Sep 02 11:47:40.960132 2020] [:error] [pid 18085] [client redacted:53136] PHP Fatal error: Declaration of syntax_plugin_blockquote_quote::handle($match, $state, $pos, &$handler) must be compatible with dokuwiki\\Extension\\SyntaxPlugin::handle($match, $state, $pos, Doku_Handler $handler) in /var/www/html/wiki/lib/plugins/blockquote/syntax/quote.php on line 0
So far I only tried a reinstall of the Plug-in, which did not help.