Both Canon and Apple have adopted HEIF / HEIC as options in their hardware (Apple since 2017). Is support for HEIF / HEIC format in the roadmap for Therapee?
While I can’t speak for RT devs and their plans, the general problem with HEIF/HEIC in any open source application is although the format itself can be easily supported (there is libheif already), the HEVC encoded content in the container unfortunately cannot because it is patent protected and not royalty-free so any decoders like libde265 are in murky waters unless they pay a license to the MPEG group.
That’s why, for example, you can install the Windows HEIF format plug-in from Microsoft Store for free, but you have to pay for the HEVC decoder plug-in.
Thank Canon and Apple for pushing patent encumbered formats instead of the royalty-free AVIF alternative.