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You can try making multiple Signal/Molly accounts with different phone numbers.
SMSPool.net is a great service for this. Cost is like $0.25 per number.
Just make sure to enable Registration Lock on each account.
By default, the phone # is the way that Signal/Molly authorizes moving your account to a new device.
Registration Lock hardens your Signal/Molly account by requiring a PIN to transfer the account to a new device, in addition to phone #. That way your accounts can't be compromised if the SMSPool phone #s get reused by somebody malicious.
Save the Signal/Molly PIN #s like you would any password.
Some related discussion in this thread:
https://discuss.grapheneos.org/d/5903-temporary-phone-numbers-for-a-multi-profile-signal-molly-molly-foss-setup
You could also try using a messaging service like Session between profiles - many of the same features as Signal, no phone # required. Have not tested personally, but you might even be able to use the same Session account on all GOS profiles, according to this chart:
https://www.messenger-matrix.de/messenger-matrix-en.html
Session seemingly has other advantages over Signal, like that it uses decentralized servers. There are disadvantages too - be sure to study the chart.
Best of luck!