Try to clear media cache and restart Telegram if there is an issue when playing audio/video.

Video with 10 subtitle tracks

MPEG-4 AVC | 2073 kb/s | 1920×1080p | 24 fps
Source: youtu.be/TcMBFSGVi1c
Subtitle: HandBrake

Video with 10 subtitle tracks

MPEG-4 AVC | 2073 kb/s | 1920×1080p | 24 fps
Sent from Telegram 5.0 (163526)
macOS Mojave 10.14.3

Source: youtu.be/TcMBFSGVi1c
Subtitle: HandBrake

Video with 10 subtitle tracks

MPEG-4 AVC | 2073 kb/s | 1920×1080p | 24 fps
Sent from Telegram Desktop 1.5.17
macOS Mojave 10.14.3

Source: youtu.be/TcMBFSGVi1c
Subtitle: HandBrake

Video with 10 subtitle tracks (MPEG-4 AVC)

MPEG-4 AVC Video
41.7 Mb/s | 3840×2160p 4K | 30 fps

Source: appsloveworld | GDrive
Sent from Telegram Desktop 2.0.1 (Windows 10)

Sample Videos-8 4k hd.mp4

How to download AV1 video from YouTube using youtube-dl

https://ytdl-org.github.io/youtube-dl/

• List all available formats ("-F" case-sensitive)
youtube-dl -F https://youtu.be/UN3uF3990Q0

Download selected video format code:

• m4a (audio only)
youtube-dl -f 140 https://youtu.be/UN3uF3990Q0

• 720p AVC (audio+video)
youtube-dl -f 22 https://youtu.be/UN3uF3990Q0

• 1080p AVC (video only)
youtube-dl -f 137 https://youtu.be/UN3uF3990Q0

• 480p AV1 (video only)
youtube-dl -f 397 https://youtu.be/UN3uF3990Q0

• 1080p AV1 (video only)
youtube-dl -f 399 https://youtu.be/UN3uF3990Q0

• 4k AV1 (video only)
youtube-dl -f 401 https://youtu.be/UN3uF3990Q0

• 8k AV1 (video only)
youtube-dl -f 571 https://youtu.be/UN3uF3990Q0

Above NYC Filmed - 480p AV1.mp4 (video only)

Sent from TDesktop 2.7.5 Windows

Above NYC Filmed - 1080p AV1.mp4 (video only)

Sent from TDesktop 2.7.5 Windows

Above NYC Filmed - 4K AV1.mp4 (video only)

Sent from TDesktop 2.7.5 Windows

Above NYC Filmed - 8K AV1.mp4 (video only)

Sent from TDesktop 2.7.5 Windows

Above NYC Filmed - audio.m4a

Sent from TDesktop 2.7.5 Windows