This sounds like a possible explanation for why I keep getting recommended different AWS client libraries from the boss to "solve instability" of a service that works 99.8% except for when the S3 endpoint (backblaze) has brief mystery issues.
May I humbly recommend Godot? It has webgl export as well as plenty of others and is fully open source, lots of language bindings as well if you don't want to learn gdscript (syntactically similar to python and honestly is pretty darned easy to work with) https://godotengine.org/