You’re not left with an “option” of an audio standard that none of your customers hardware or browsers support.
Additionally, being an open standard, you can probably rely on ffmpeg supporting it. This allows you to transcode into something that your proprietary encoder will support for ingest if it comes to that.
This is also ignoring the first sentence: your whole supposition is based on a scenario where you as the content producer for some reason encoded in a format that your customers don't have, and don't have the masters for some reason. Which is basically absurd for anything that would need dynamic HDR or spatial audio.