Apple silicon. If you have 0.2.21 or earlier, download this once, drag Pebble to Applications and choose Replace. From 0.2.22 on, Pebble updates itself.
Windows may show a warning because this installer isn't signed yet. Choose More info, then Run anyway. Updates are not automatic on Windows yet; new versions come from pebble.bot.
Debian / Ubuntu: sudo apt install ./pebble_0.2.22_amd64.deb
AppImage: chmod +x, then run. Updates are not automatic on Linux yet.
0.2.22 is x64 only. Arm64 Linux stays on 0.2.17.