>streamlink -l debug https://www.mildom.com/10148036 best
[cli][debug] OS:         Windows 10
[cli][debug] Python:     3.7.5
[cli][debug] Streamlink: 3.1.1
[cli][debug] Requests(2.26.0), Socks(1.7.1), Websocket(1.2.1)
[cli][debug] Arguments:
[cli][debug]  url=https://www.mildom.com/10148036
[cli][debug]  stream=['best']
[cli][debug]  --loglevel=debug
[cli][info] Found matching plugin mildom for URL https://www.mildom.com/10148036
[cli][info] Available streams: 144p (worst), 360p, 540p, 720p, 1080p (best)
[cli][info] Opening stream: 1080p (hls)
[cli][info] Starting player: "C:\Program Files (x86)\VideoLAN\VLC\vlc.exe"
[stream.hls][debug] Reloading playlist
[cli][debug] Pre-buffering 8192 bytes
[stream.hls][error] Unable to open URL: https://txlvb-play-hls.mildom.tv/live/10148036.m3u8 (403 Client Error: Forbidden for url: https://txlvb-play-hls.mildom.tv/live/10148036.m3u8)

>streamlink -l debug https://www.mildom.com/10148036 best
[cli][debug] OS:         Windows 10
[cli][debug] Python:     3.7.5
[cli][debug] Streamlink: 3.1.1
[cli][debug] Requests(2.26.0), Socks(1.7.1), Websocket(1.2.1)
[cli][debug] Arguments:
[cli][debug]  url=https://www.mildom.com/10148036
[cli][debug]  stream=['best']
[cli][debug]  --loglevel=debug
[cli][info] Found matching plugin mildom for URL https://www.mildom.com/10148036
[cli][info] Available streams: 144p (worst), 360p, 540p, 720p, 1080p (best)
[cli][info] Opening stream: 1080p (hls)
[cli][info] Starting player: "C:\Program Files (x86)\VideoLAN\VLC\vlc.exe"
[stream.hls][debug] Reloading playlist
[cli][debug] Pre-buffering 8192 bytes
[stream.hls][debug] First Sequence: 1342; Last Sequence: 1351
[stream.hls][debug] Start offset: 0; Duration: None; Start Sequence: 1349; End Sequence: None