Sometimes, the service provider may route your traffic through an efficient path to league of legend server and that may add additional pings and ping spikes to your game.
To fix this, you can try using a VPN server that is specifically designed to optimize your gaming experience (eg. Express VPN). However, before you reach the VPN server, the traffic is still determined by your internet provider. If using a VPN server still doesn’t work, maybe your best option is to switch to a better internet provider.
The How To Guide 