Replace a specific URL on all apperances on the Website (Maybe a filter?)

I’m stuck with this problem:

The Plugin "Lazy Load – Optimize Images" is doing a great job lazy loading YouTube-Videos but is automatically using a preview picture from the YouTube-Server. The Server ist very slow and when I show a Video above the fold it really drags the page speed insights rating down.

Is there a way to replace the URL manually after the plugin created it’s part of the html-code? Like a filter I can use? Of course I know the URL-String i want to replace..

(The creator of the plugin didn’t provide a solution for that question in the support forum, so I’m hoping for a solution from you guys 😉 ).