Birch  you are partly right the installation of una does not include php.ini files is why you get this message php.ini files are server files and thus can be used to turn of allow_url_include to turn it off you just need to set up a php.ini file and add it to the right files

for example when i manually installed una i had to add a php.ini file to install directory to install it as allow_url_include was on i had to turn it off i did so with a php.ini file same with studio i could not access studio i added that same php.ini file to studio sorted same with not being able to have the time line post or being able to access conversations section of the site i added a php.ini file to modules folder sorted and i originally had a php.ini file in the root directory of the site so the user side was accessible without this warning

from this website you will read the same as what Birch posted but heres how to solve your issue Muhammad Zahid Ali 

https://yomotherboard.com/risk-phps-allow_url_include-enabled/

P.S. Muhammad Zahid Ali Post what page your having this problem on so we can better help you as the php.ini file needs to be added to the right place with the command from the above website or you could contact your hosting company if there a good host they should be able to fix it within the hour