As far as I know non of those features are available to use in three.js, at the moment, but there have been some long standing PRs to add the functionality.
- Transform feedback by @fernandojsg: [WIP] [WEBGL2] Transform feedback by fernandojsg · Pull Request #14503 · mrdoob/three.js · GitHub
- MRT by @takahirox: https://github.com/mrdoob/three.js/pull/16390
- UBOs by @mugen87: WebGL2: Added support for Uniform Buffer Objects. by Mugen87 · Pull Request #15562 · mrdoob/three.js · GitHub
I believe there are other PRs, as well. WebGL2 has had a bit of a rocky rollout particularly with Apple still not supporting it on any of their browsers. I believe the plan is to wait until WebGL2 is supported everywhere before adding any WebGL2 specific features.
I asked a bit about this earlier last year and this was @mrdoob’s response:
I’m not sure if thoughts have changed at all since with WebGPU now on the horizon, though. It’s still crazy to me that Apple has stalled WebGL2 for so long. I’d really like to be able to use these new features, too.