See also Mastering workflow for linear images for HDR displays, Experimenting with HLG and HDR10 for still images, Processing RAWs for HDR displays in Darktable, and Exporting images for use in HDR TV production
Sounds like this topic can even be merged in there somewhere… @paperdigits
Also, might be worth splitting your problem in two and tackling it piece by piece: AVIF output from darktable (using e.g. known HDR images like the EXR samples in other topics cf. testing your Chrome w/ known files), vs the unknown “linear TIFF” input.