No one asked for this, but have you thought of running Carla and plugins on the browser?

I have been studying and testing web assembly recently, using emscripten to compile regular C++ code.
There are quite some restrictions and quirkiness (everything runs on the main thread, even audio), but with some effort it is possible to make it work.

First real test, Ildaeil-Synth.
https://falktx.com/data/wasm/Ildaeil-Synth.html

1. select "Audio File" from the list
2. click "Load plugin"
3. enjoy some music