I tested near KSBB. There are four test streams being broadcast in HEVC/AC4.
The video is watermarked "NPG ATSC3 Channel 17.x" on the top right:
The streams appear to all be NPG owned stations:
17.1 MyTV (Santa Barbara)
17.2 News-Press NOW (Missouri)
17.3 KIFI (Idaho)
17.4 KESQ (Palm Springs)
Broadcast specs are as follows:
17.1: 1080p 5.5mbps
17.2-17.4: 720p 4mbps
And the libhdhomerun session:
tmm1-ipadpro:~/libhdhomerun# ./hdhomerun_config 169.254.57.127 set /tuner0/vchannel 17.1
tmm1-ipadpro:~/libhdhomerun# ./hdhomerun_config 169.254.57.127 get /tuner0/status
ch=atsc3:491000000:0 lock=atsc3 ss=59 snq=90 seq=100 bps=0 pps=0
tmm1-ipadpro:~/libhdhomerun# ./hdhomerun_config 169.254.57.127 get /tuner0/debug
tun: ch=atsc3:491000000:0 lock=atsc3:491000000 ss=59 snq=89 seq=100 dbg=26-96/936
dev: bps=20406272 resync=0 overflow=0
ts: bps=0 te=0 crc=0
net: pps=0 err=0 stop=0
tmm1-ipadpro:~/libhdhomerun# ./hdhomerun_config 169.254.57.127 get /tuner0/plpinfo
0: mod=qam256 cod=11/15 bond=0 layer=core ti=cti lls=1 lock=1 errs=0
tmm1-ipadpro:~/libhdhomerun# ./hdhomerun_config 169.254.57.127 get /tuner0/streaminfo
4353: 17.1 ATCst1
4354: 17.2 ATCst2
4355: 17.3 ATCst3
4356: 17.4 ATCst4