hi... i have no good news!
I confirm that the stock media player send correctly metadata over bluetooth, with xiialive i tryed both option AVRCP MetaData OFF and ON, with Lockscreen control option always set to on and that's what happens:

with AVRCP MetaData ON i can switch from track title, artist and album name but i can read on the car radio: NO TITLE, NO ARTIST, NO ALBUM...
with AVRCP MetaData OFF i can read on car radio display "0" as track name, and i cannot switch between other information

in 2015 i had a wiko rainbow with the same car radio and metadata were displayed properly... so now i changed only the smartphone...

if can i do something else to help you please let me know !

thanks a lot !

the stock media player send metadata properly... this evening i will try AVRCP metadata OFF because i have set it to ON... I had bed interpretation of this... sorry
i write back tomorrow moring, thank you soo much

sorry... metadata still non being displayed... how can i help you ?

bug report sent, with this URL as comment, hope this help !!!
please let me know if i can give more support to solve the problem !

hi! i have a Sony Automotive car radio... it's capable to display metadata because i can read it via Android Stock MediaPlayer and... with my previous smartphone (Wiko Rainbow Kitkat), metatada were displayed also on xiialive!
The AVRCP settings are ok... also the lockscreen but, i notice that sometimes the lockscreen control does not appear on my lockscreen...
hope this help to solve the problem !