[lxgr]

Displayport to HDMI 2.1 adapters already seem quite complex: https://www.paradetech.com/products/ps196/

Is the problem expressing the maximum supported bandwidth end-to-end, i.e. not as a function of the DP channel quality that the source sees?

[brigade]

Yes, as a specific example, if the HDMI sink wants DSC, maximizing the quality (minimizing the compression ratio) fundamentally cannot be done without knowing the end-to-end bandwidth.