Where can I find the ffmpeg LGPL source code for Clipchamp's changes ?

Question

ffmpeg is licensed under the LGPL or GPL.

I noticed that Clipchamp uses a modified copy of ffmpeg: ffmpeg-simd.wasm,

the LGPL requires that the changes be open source, where can I get the modified ffmpeg source code?

Or maybe my understanding of the LGPL open source license is incorrect, please help me correct.