In prior versions of the launcher, after choosing a profile / installation, it would remember that choice. In the future, pressing the large, green "Play" button would continue to launch the same profile / installation. In the current version, this is not the case. Each time the launcher starts, it selects the "Latest Release" installation. Each time, I change the selection to my preferred installation. The next time I start the launcher, it has forgotten my prior selection. I much preferred the old behavior where it remembers your preferred installation between starts of the launcher.
I suspect this is the same issue as https://bugs.mojang.com/projects/MCL/issues/MCL-12075