How do you do this technically? Shutting down phone and router (so many things complain when no WiFi, you need a phd to disable iPhones), alarms, and still a way to be reached in case of emergency?
The mere presence of a smartphone reduces basal attentional performance
https://www.nature.com/articles/s41598-023-36256-4
The only thing I missed was documentation, so I downloaded offline docs. Then occasionally I missed Google. So I just kept a list of stuff to Google an hour or two later when I came back online.
I made sure my work was full of variety so if I got completely stuck on one task (rare), I could just switch gears.
Most devices might complain, but most will simply stop working silently and then reconnect when they have a chance. Some might need to be power cycled because they gave up trying to connect (I had a smart garage door that had bad connectivity and would sometimes do a version of this).