Your URL appears to resolve to a workable stream, but the .m3u8 does not contain a direct link to a transport stream,
you'll need to pipe it through ffmpeg.
Try creating a local .m3u8 file containing:
#EXTM3U
#EXTINF:0,Channel Name
pipe:///usr/bin/ffmpeg -loglevel fatal -i https://ws.hls.nimo.tv/live/su1599512427609rec4c3a4d7d72c1946e09a8d6ca157304_high/playlist.m3u8 -map 0 -copy_unknown -c copy -metadata -f mpegts pipe:1
Replace "Channel Name" with an appropriate name.
In the URL section of your network, change the URL to
file:///path/to/file.m3u8
Replacing /path/to/file.m3u8 with the actual path to your file, and yes that is supposed to be 3 slashes after file:
If you still have trouble scanning, try increasing the scan timeout.