I got the Xiaomi 9T Pro (variant of the K20 Pro) when it was released, it's one of the very few phones that fulfill my criteria for a phone that would last a long time

  * Repairable (modular design, pull-tabs for battery)
  * Good build quality (JerryRigEverything approved)
  * Rootable
  * Stable software, with long term vendor software updates
  * Active community for ROMs (if the vendor stops supporting the phone)
  * 3.5mm jack (with an excellent DAC)
  * Relatively compact
  * Flat screen, no notch/holepunch. Curved screens are more fragile and are more expensive to replace.
  * Good battery life
  * Spare parts available (e.g. main camera for $15 shipped)
  * Cheap
  * Decent processor, RAM and storage

There are some downsides, so not for everyone:

  * Comes with bloatware, some of it can only be disabled with root
  * Rooting is a pain
  * Spare parts in China, so might take a while to arrive
  * Launcher is not great, but can be easily replaced
  * Camera is not best in class

In the same situation here, have an iPhone 11 that is due to be replaced.

The iPhone 12 is lighter but has worse battery life, so that one is out.

The Sony Xperia 5 II is the current favorite as it has very good battery life and no annoying notch.

And the recent Apple vs Epic case is making the switch easier.

I'll definitely consider a Sony for my next purchase. I wish they'd bring back that super-compact design they had years earlier.

The current display tech required for a compact phone is quite expensive at the moment.

Some phones do exist already such as these:

Samsung Galaxy Z Flip 5G https://www.samsung.com/us/mobile/galaxy-z-flip/

Motorola razr 2020 https://www.motorola.com/us/smartphones-razr