BTW, in Molly's settings, you can go into the settings (Vertical 3 dots > Settings > Help > Toggle the "Auto-update Molly" switch off and then on) to "manually" trigger a Molly update, if you know that there's a released update but the app hasn't checked yet.
IIRC, the Signal website APK doesn't have options/menus to trigger any form of update. You basically pray that the update will come when the website APK automatically checks for updates on its own.