Just want to confirm this same thing happened to me. I had been daily driving calyxos, but wanted to give the new 24.04 a try. Initial progression went like this:
calyxos > fairphone 15 > ubuntu 24.04 - neither wifi nor T-Mobile data worked
I messed around with a couple other things including postmarket, no avail. Tried your trick:
postmarket > fairphone 13 > changed setting above > ubuntu 24.04 - wifi and LTE both work
Strange, and I'm not sure I follow why that works, but can confirm it does. Thanks!