Also worth mentioning that you can set auto-reboot to a shorter period (down to 10 minutes). So if you anticipate situations where your phone can be seized (border crossings, demonstrations), it's worth temporarily setting this to a short time period (or rebooting your phone yourself to get to BFU).
Delete the contact book? Clear calendars?
Where exactly should one stop?
Not even kidding here, it's time to bring out thin client computing to cellphones. Let the spicy stuff sit somewhere else. I could bootstrap a Tailscale or Netbird signin remotely, install the access client, and remote back into the 'normal phone'.
Would be then funny to map that to lockscreen PINs - enter a PIN to unlock the device, be remoted into "phone A", enter another pin and be remoted into "phone B", enter another PIN and you're on the 'local device' session. (Or duress-PIN kill "phone A" if someone attempts to bruteforce PINs, etc, etc...)