Results from https://wasm-feature-detect.surma.technology/ is following:
| ✔️ | bigInt |
| ✔️ | bulkMemory |
| ✔️ | exceptions |
| ✔️ | extendedConst |
| ❌ | gc |
| ❌ | jspi |
| ❌ | memory64 |
| ❌ | multiMemory |
| ✔️ | multiValue |
| ✔️ | mutableGlobals |
| ✔️ | referenceTypes |
| ❌ | relaxedSimd |
| ✔️ | saturatedFloatToInt |
| ✔️ | signExtensions |
| ✔️ | simd |
| ✔️ | streamingCompilation |
| ❌ | tailCall |
| ❌ | threads |
| ❌ | typeReflection |
All "wasm" options in about:config except "javascript.options.wasm_verbose" is true.
I'm not familiar with Godot engine to file any bug reports.