I need to know what font is used here

Trade Gothic Bold Condensed No. 20  Suggested by KeziahBlue 
Youtube Sans  Suggested by marty666 
Alternate Gothic No 2  Suggested by gonfer00 

It's this font

https://www.dafont.com/forum/read/331806/new-youtube-logo-font

Youtube Sans is a different font from that of the logo

https://www.itsnicethat.com/news/youtube-sans-typeface-by-saffron-190517

https://www.itsnicethat.com/system/files/052017/591ec0487fa44ca09f0002b0/images_slice_large/YouTube-Sans_0.jpg

It's Alternate Gothic 2, as it's explained in the thread you quoted

https://www.theverge.com/platform/amp/2017/8/29/16216868/new-youtube-logo-redesign-font-color-app-design

'Once they had decided to keep the play button and wordmark, the team set about modernizing them. “The old logo has a typeface from 1903, alternate gothic number two, and it’s been manually tweaked, so there are weird design nerd things that are off. The U in Tube is not the same as the U in You, so if you take them and overlay they don’t exactly line up,” said Bettig. '

https://www.dafont.com/forum/read/331806/new-youtube-logo-font