A clean installation of admintools on a site with the core htaccess plus the following code from my host
<FilesMatch \.php$>
SetHandler proxy:fcgi://brian-php80
</FilesMatch>
Running the quickstart wizard resulted in
Warning: Invalid argument supplied for foreach() in /home/brian/redacted/administrator/components/com_admintools/src/Model/HtaccessmakerModel.php on line 305