In Dolibarr version 8 to force SSL you need to change in config.php file as Eldy said
$dolibarr_main_force_https='0';
to $dolibarr_main_force_https='https://yourdomain.com/';
Iām pretty sure that applies to all Dolibarr versions.
Just change the .htacess file
write on it:
RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://www.yourdomain.com/$1 [R,L]
which one be more specific please