Android Nougat 7.1.2
Latest LinageOS + microG 14.1 update (29/02/2019) :
[https://download.lineage.microg.org/piccolo/]
Latest unofficial update (23/12/2019) : [https://www.android-hilfe.de/forum/bq-aquaris-m5.2274/weitere-updates.877065-page-3.html]
HTCMania Forum : https://www.htcmania.com/showthread.php?t=1488515
Firmware : https://www.bq.com/en/support/aquaris-m5/support-sheet
Thank You !