I'm not sure what you're referring to, but what I basically do is self-host everything that stores relevant data: Vaultwarden, Immich, Notesnook, etc. I only know how to set up Bitwarden and my 2FA generator from scratch, so when I get a new phone, I install Bitwarden and the 2FA app and set them up.
Then everything else is documented inside Bitwarden. It's just a matter of installing the apps and logging in using the credentials stored in Bitwarden and a 2FA token generator.
There's no need for relying on any phone OS features.
This seems to describe a workflow with a small number of apps that store things remotely.
I want to back up my phone and restore it in one step, possibly to different hardware, and have it work like nothing ever happened. I can do that with a PC. I ought to be able to do that with a phone too.
I'll use Signal as my example of an app that's especially annoying to deal with in the border crossing scenario. I want to back up Signal and install it on a clean device without losing messages, changing my safety number, or verifying by SMS with a phone number I may not have access to at my destination. It's not possible, though I'll grant some of that is design choices made by Signal rather than the operating system.
I have to use its built-in backup function to keep my messages; if I just copy the data, it can't decrypt because the keys are in the old device's TPM. Even with the backup and password, I have to use SMS verification. Finally, the safety number seems to be tied to the keys in the old TPM, so I there's no way to do this without changing it and annoying my contacts (or teaching them to ignore safety number changes).
Makes sense, thanks for explaining!
You still have to set all that up.