I bought a Flarm Atom UAV transceiver which works much more reliable than my DIY transceiver. And it receives not only Flarm signals but also ADS-B signals. Tech specs here: Atom UAV – FLARM for Drones | FLARM Technology
I really like this little thing. Comes with two antennas and one GNSS receiver. But it can use the GNSS signal from the autopilot via Mavlink as well!
This one is certified
Also check uAvionix
p.s. in your original post you said manned aircraft with ADS-B fly above 32000ft.
“ For aircraft operating at or above FL180 (18,000 feet), you must be equipped with a Mode S-transponder-based ADS-B transmitter. For aircraft operating below 18,000 feet and within U.S. airspace, you must be equipped with either a Mode S transponder with Extended Squitter or a Universal Access Transceiver (UAT).Apr 15, 2022”
Hello, could you please tell us what ESP32 board you are using and to what pin you connected TX and RX from the Ardupilot Mavlink port ?
So far, I did not get SoftRF to work in UAV mode (I succeeded in Normal mode), I tried different pin options (I believe the Mavlink v1 stream should be connected to UART1 @57600, but not even sure)… 
Thanks a lot
Hello, could you please tell us what ESP32 board you were using and to what pin on that board you connected TX and RX to the Ardupilot Mavlink port ?
So far, I did not get SoftRF to work in UAV mode (I succeeded in Normal mode), I tried different ESP32 pin options (I believe the Mavlink v1 stream should be connected to ESP32 UART1 @57600, but not even sure)…
Thanks a lot