When using a third party SMS app (e.g., QUIK/QKSMS) in the admin profile and then the stock SMS app in the non-admin profile(s), a text from the non-admin profile will automatically get duplicated.
For example, if you send the word "test" to an arbitrary contact from the non-admin profile (on stock messaging app), you will see that the following actually got sent to your contact:
"test
test"
So one alternative would be to switch to a third-party app in the non-admin profile. The issue then becomes that the third-party app doesn't automatically sync from the android sms database, as explained in this post: https://discuss.grapheneos.org/d/9674-qksms-not-automatically-syncing-messages.
Anyone have any insight into fixing the duplicate messaging issue?