SailfishOS should have support for additional higher quality bluetooth A2DP audio codecs. Currently (as of sfos v4.0) only the basic mandatory SBC codec is supported with bluetooth A2DP.
Optional A2DP codecs such as AAC, AptX, AptX HD, and LDAC allow using bigger bitrate and/or higher quality than the mandatory/default SBC codec.
sfos currently ships bluez v5.54, which in theory has the initial support for using and switching multiple bluetooth A2DP audio codecs, but it’d be good to upgrade to latest bluez version (v5.58+) where A2DP codecs functionality is known to work properly on desktop/laptop Linux, as there have been multiple related bugfixes since version 5.54.
Pulseaudio 15.0 will have support for multiple bluetooth A2DP codecs (when used with current bluez, and additional codecs are available). Currently pulseaudio 15.0 is still in development, and the final version hasn’t been released yet, but the multiple bluetooth A2DP codecs functionality is already merged and working.
Pulseaudio 15.0 also has support for higher quality bluetooth backchannel / microphone in HFP mode by using optional mSBC codec (also known as Wide Band Speech). mSBC allows using 16 kHz samplerate, which is much better quality than the 8 kHz samplerate with the default CVSD microphone codec.
Pulseaudio 15.0 also enables using multiple SBC codec profiles/bitpools in A2DP mode, allowing higher quality also with the mandatory SBC codec.