LOL (pun intended) - unauthorized third party modification to the game that magically makes it perform better on sub par hardware.... right... Are you on a laptop with with a video card that uses shared memory like an Intel 4MB?
No explanation of how or why it works at all.
I browsed through the source code and do not see any attempt to steal credentials or anything else malicious, but it is also not doing anything that will magically fix your issue. I can delete league client text logs, allow software through windows firewall, how is this related to FPS? This reminds of of all the magic devices that claim to increase fuel mileage in cars. If the magic devices worked why wouldnt manufacturers be using them in order to gain an advantage over competitors?
The only solution to your fps issue is better hardware.
https://boards.euw.leagueoflegends.com/en/c/help-support-en/8TEZEdkB-warning-to-all-using-lolupdater-dont-use-it-you-will-get-banned