If you have Spotify, you might want to listen to a new recording of Mahler's 1st from Kamioka / New Japan Philharmonic. The portamento throughout is... well, I'm not sure how to describe it. Certainly, you won't miss it. Do listen if you have a chance:
https://open.spotify.com/album/2UQ1ghXqiMvgvHPLpE19oE