Thanks, the issue seems fixed in the newest zip. Running ldd on ./Vamp shows the supplied SDL2 library is being preferred first.
I have one other issue/question. Where did you get your SDL2 shared lib from? It seems to be causing an issue that renders my monitor unusable when the game enters fullscreen. Using my system-provided SDL2 allows fullscreen to work.
I remember running into this issue with my own game when I compiled SDL2 myself without having some X11 libraries installed.
If you're not already doing this, you should probably be getting the SDL2 library from the Steam Runtime, which is what that the SDL wiki also recommends ("known good", it's called).