From https://github.com/dectris/documentation/blob/main/cbor/dectris-compression-tag.md#lz4-hdf5-framing , https://support.hdfgroup.org/services/filters/HDF5_LZ4.pdf is 404. https://github.com/dectris/HDF5Plugin/blob/master/HDF5_LZ4.pdf seems to be a valid copy of it, though I don't know if you have any specific preferences.
From https://github.com/dectris/documentation/blob/main/cbor/dectris-compression-tag.md#lz4-hdf5-framing , https://support.hdfgroup.org/services/filters/HDF5_LZ4.pdf is 404. https://github.com/dectris/HDF5Plugin/blob/master/HDF5_LZ4.pdf seems to be a valid copy of it, though I don't know if you have any specific preferences.