If this is still the main thread for aftermarket units...
I installed the Grom Vline in my 2017 LC about a month ago. I live in the city/street park and this was easy enough for me to do in about 1.5 hours. Note they don't have a full video for the 2016-2018 LC, so you have to use the video for the 2015-2018 LX570 for the Grom Vline install and the video for the 2019-2021 LC for dash removal/reinstall.
When it works well, it's great... boots up really quickly/no noticeable lag over stock nav system and works totally seamlessly, including steering wheel controls and voice commands. That's about half of the time so far.
About a quarter of the time, it doesn't find my phone at all and I have to revert to factory nav/radio. A (car) restart may help correct the issue, but not always.
The other quarter of the time, the system works fine except there's no sound comes out of it, either from music sources or connected phone.
I'm stilling working through the gremlins (Gromlins...?). Support has been prompt each time thus far, and I'm trying to keep an open mind, but it's a little frustrating.
Update June 6: it has stabilized somewhat. Generally always finds my phone (or my wife's) now. Maybe 25% of the time, the sound doesn't work... Carplay works, nav works, songs appear to be playing, but there is no sound transmitted. Usually fixed with a restart.
Update June 28: touch wood, it has totally stabilized now and generally always finds my phone, though it prefers my wife's even if she gets in the car up to 5-10s after me. Sound works consistently now. Getting to the point I would recommend it now!