This won't help you, since it seems you're looking for a "one-button-push" solution. I don't think you'll find it since I've found that such convenience is lost when gaining more privacy and security. Even with laptops/desktops.
I've accepted and live well with the fact that I have ephemeral messaging history, etc. Trying out new mobile OSes on my "main phone" in the past has also made me live through that a few times.
Additionally, I try to install and use the minimum amount of apps as possible on my phone.
For the important files and photos, I also have a Nextcloud self-hosted server with sync and everything else that's important in terms of setup is documented (in files synchronitez to Nextcloud too), so when I have to setup a new phone it's just following along a document I wrote.
The only "interesting" thing I lose when replacing my phone is a couple of hours and a recent-looking gallery and Signal messaging history.