[keithwinstein]

Opus does support adaptive bitrate audio and in basically the same way; with the reference encoder, you can use OPUS_SET_PREDICTION_DISABLED to create a stream access point.

Loudness management isn't really the purview of the decoder/compressed format itself; the article describes using MPEG-D DRC which is, at least in principle, independent of the choice of xHE-AAC vs. Opus. To be clear I have no idea how companies do dynamic range compression in practice; in the Web setting, maybe via stuff like https://developer.mozilla.org/en-US/docs/Web/API/DynamicsCom... etc.?