"Simply update your address with the post office and you're done."

Welcome to the 19th century! Which is when mail redirection to a new address was introduced in the UK. I'd be amazed if it wasn't around then or earlier in the USA as well. Simply fill out a form and your mail will be redirected for up to two years (albeit at a cost). Or use a PO box and a mail forwarding service which offers filtering of junk mail. I used one for years when I used to move around a lot for less than £100 a year.

> Welcome to the 19th century! Which is when mail redirection to a new address was introduced in the UK.

That’s not the same thing. Everyone still has your old address and you need to update it with them. Not terribly painful if you move once every 5 years. Pretty annoying and error prone if you move every 6 months.

Hence option 2 - the PO box.

Which is rejected as a valid address by many banks, government forms, etc. I want something that the post office guarantees has a real person behind it so I can use it for literally everything that requires an address.

I do this, any bureaucratic organization that I want to be able to reach me (very very few) gets my PO box, which has remained the same across three addresses.

The US has mail forwarding for 1 year, but that doesn't solve the problem, as you still need to update the source information with all the companies. I usually end up spending several hours changing addresses when I move. It's better to do this right away than to rely on the forwarding completely. Some places get the change of address info automatically and update their records, but it's never the ones you actually want (usually catalogs and marketing mail).

A PO box would be fine, but it's not an acceptable address with many businesses, so it's not a universal solution to the problem.

A workaround for some forms that don't accept PO Boxes:

Type something like P0 B0X

Type the address of the post office and then the PO Box number like an apartment number