I used Gaia on my recently climb on the 17th the entire way through, on Airplane Mode. Recorded my every mode never had any GPS signal lost.

Yes, there is cell reception at the Summit, but is spotty but I was able to post on IG/FB where I was sitting at the summit.

For the most part, trail is straight forward (now, at least). It wasn't, couple weeks ago, when I went. I needed the GPS for a little bit when I go to the Mirror Lake area heading up to the left of the rocks but other than what, pretty visible and clear.