"If you wish to use the same phone number for both Molly and Signal, you must register Molly as a linked device. Registering the same number independently on both apps will result in only the most recently registered app staying active, while the other will go offline."
Yeah, pretty sure that's what me and the other comment meant. Linked device, like using Signal on Desktop. Or Signal on iPad. Linking wasn't available on Signal for Android for some reason.
Specifically I'm using Signal as the main device, with Molly as the linked device on 2nd phone.
"If you wish to use the same phone number for both Molly and Signal, you must register Molly as a linked device. Registering the same number independently on both apps will result in only the most recently registered app staying active, while the other will go offline."