My setup (following Schneier's essay 'data is a toxic asset') is as follows: 1 week self-destructing messages in Signal (I don't use WhatsApp). If its an important message I save it (can't remember the last time that happened), if its an important picture I save it (which then gets uploaded to Nextcloud, which gets backed up to a Synology elsewhere, and it gets deleted from my smartphone but available via Nextcloud; e.g. photo as memory of our young children). There's no data to save, no data to migrate (I also don't use Google Drive for backups) and the only data there automagically gets removed within a week. My Nextcloud is only reachable via Wireguard. If my smartphone gets compromised (ie. stolen or lost) I'd need to revoke that keypair in Wireguard.
> the only data there automagically gets removed within a week
Nice! To be clear, you can't count on the same thing happening on the other end of the connection due to various alternative Signal clients. This is kind of where Snapchat is king of the hill, but obviously nothing is perfect!
Snapchat APK can be modded, with root one can make screenshots and videos (I believe it is how some revenche porn is made). There's also analog screenshots (photos), and the end point (smartphone) can be hacked e.g. contain malware.
In my M.O. I assume the end point is not compromised and is honest; otherwise, whatever I write can be traced back to me.
Best thing would be not saying it, but if you were to make a good setup it wouldn't involve Android or iOS but something like Tails. And yet, we know deployed military in Ukraine don't use such. But what they do is better than analogue Russian on 8900 MHz.
