I don’t think any of the recommendations here are even close to what OP is asking for… QUIK from my understanding is just a replacement SMS app, it does not “sync messages to other devices” or allow you to send SMS messages via your phone from other devices, nor does it have a desktop/web version, all of which is what Message+ does. Pretty sure this requires a self-hosted server to do (or a third-party proprietary service like MightyText).
SmsMatrix, KDEConnect/GSConnect, Nextcloud Talk are some examples that will do this.
I think if syncing of (at least) upstream histories between clones was done automatically, they might consider that more in-line with their definition of decentralized.
Also kudos to both of you for communicating your differences properly without resorting to arguments.
I feel like so much of the arguing and trolling nowadays is simply due to a difference in subjective definitions and people not being able to calmly communicate that with each other.