1) Installer is at admin/install/index.php
2) Select "MySQLi" for Database type in manual installation.
3) Move USING BTREE to the left and not at the end.
4) Check everytime "define('DC_CRYPT_ALGO','sha512');" in inc/config.php If it has changed then check password method. Because we have added hardcoded 'sha512' in password method. Since 2.12 version.
5) PHP REQUIREMENT LINK: https://github.com/dotclear/dotclear#requirements
6) Currently we have set PHP 8.0 as min requirement in info.xml due to syntax error on PHP 7.4 (while visiting frontend, change req in info.xml to 7.4, if vendor pushes fix for the same)