Update on my difficulties with navigation uploads & bluetooth connectivity.
Previously I was running Android 5.1. A year or two ago this worked great but recently I have been having massive problems maintaining Bluetooth connectivity and uploading routes longer than say 20 miles.
When I contacted Lezyne tech support they suggested upgrading the Android operating system. This is a great idea in theory but not every device can upgrade and even if it can, it's a pretty big project.
So I tried operating the device on my wife's phone, which is Android 8. This was noticeably improved over my phone, but still maybe 80%, not 100%. I could load maybe a 60 mile route to the device OK. But it was a moderate improvement, not a complete solution, which put me off upgrading my own phone until just recently.
So I put my phone on Android 9 and--wah-lah. The problems are solved.
I can upload 120 mile route. It maintains Bluetooth connectivity throughout a ride and auto-downloads at the end. It send along all notifications & messages I've requested. It's basically as good as it was when it--and my phone--were new.
So my guess is, they test only on the **latest** operating systems.
As long as you're on the latest & greatest, you'll be OK. The further you diverge from that, the worse off you'll be.
I can understand why the do that--testing is difficult and expensive, and there are currently no fewer than EIGHT Android versions with > 5% of the market.
Plus I don't even know how many iOS versions.
But they are somewhat cooking their own gooses, because what happens if you are running Android 4, 5, 6, 7, or 8 (which amounts to like 90% of the market!) then your Lezyne will work somewhere between barely, slightly, and mostly with various features randomly breaking and no one really know why.
If you're on Android 9 you'll probably be quite delighted and wondering why everyone else is kicking up a fuss.
FWIW.
See current Android versions with market share here: developer.android.com/about/dashboards (still can't post URLs, sorry)