If "fsockopen" is deactivated on a webspace, the following error message appears under PHP 8 in the ACP

 {{Fatal error: Uncaught Error: Call to undefined function phpbb\fsockopen() in /users/**/www/forum2/phpbb/file_downloader.php:45 Stack trace: #0 /users/*/www/forum2/phpbb/version_helper.php(384): phpbb\file_downloader->get('version.phpbb.c...', '/phpbb', 'versions.json', 80) #1 /users/*/www/forum2/phpbb/version_helper.php(354): phpbb\version_helper->get_versions(false, false) #2 /users/*/www/forum2/phpbb/version_helper.php(230): phpbb\version_helper->get_versions_matching_stability(false, false) #3 /users/*/www/forum2/includes/acp/acp_main.php(447): phpbb\version_helper->get_update_on_branch(false) #4 /users/*/www/forum2/includes/functions_module.php(676): acp_main->main('main', 'main') #5 /users/**/www/forum2/adm/index.php(81): p_master->load_active() #6

Unknown macro: {main}

thrown in /users/***/www/forum2/phpbb/file_downloader.php on line 45}}

Everything works under PHP 7.4.2.
This fix helped.