Popolon's post in Enabling ROCKCHIP_DW_DP on RK3588 based devices to have working HDMI0 (next to HeadphoneJack one on a Rock 5 ITX) was marked as the answer
Works just fine on last version. Looks like need to Login on Wayland/X11 first, not sure. Thanks a lot !!!
<pre>
$ zcat /proc/config.gz | grep DP| grep ROCK
CONFIG_ROCKCHIP_ANALOGIX_DP=y
CONFIG_ROCKCHIP_CDN_DP=y
CONFIG_ROCKCHIP_DW_DP=y
CONFIG_PHY_ROCKCHIP_DP=y
CONFIG_PHY_ROCKCHIP_DPHY_RX0=m
CONFIG_PHY_ROCKCHIP_INNO_CSIDPHY=m
CONFIG_PHY_ROCKCHIP_INNO_DSIDPHY=m
CONFIG_PHY_ROCKCHIP_SAMSUNG_HDPTX=m
CONFIG_PHY_ROCKCHIP_USBDP=m
CONFIG_PHY_ROCKCHIP_DP=y
</pre>