FiiO「M17」ファームウェアアップデートのご案内 – Fiio Japan
FiiO「M11 Plus ESS」ファームウェアアップデートのご案内 – Fiio Japan
FiiO「M11S」ファームウェアアップデートのご案内 – Fiio Japan
FiiO「M11 Plus LTD」ファームウェアアップデートのご案内 – Fiio Japan
日本語情報が来てたんで追記

The new firmware for M17/M11S/M11 Plus LTD/M11 Plus is now available!-FiiO---BORN FOR MUSIC
M17 Ver. 1.0.6
M11 Plus Ver. 1.0.3
M11S Ver. 1.0.2
M11 Plus LTD Ver. 1.0.8
・ Added ROON Ready function (on desktop screen or click the FiiO Roon in the drop-down menu to use);
・ Added LHDC codec support for Bluetooth transmitting;※M11S以外
・ Added second harmonic regulation function (can be set in the Settings - Audio - Second harmonic regulation);※M11 Plus LTD以外
・ Added experimental functions (PEQ, DLNA transmission);
・ Added support for DTS format;
・ Added desktop icon shortcuts for FiiO Music (multimedia service, local music, playlists, continue);
・ Fix the display error of sampling rate on the status bar when playing music using third-party apps.); ※M11Sのみ
・ Fixed display problem of some MQA tracks;
・ Fixed the issue where a few tracks might not be played correctly;※M11 Plus LTDのみ
・ The tracks in the DLNA album directory are changed to be sorted by track numbers;
・ Miscellaneous improvements in performance.