The iOS update is temporarily unavailable

Sednout wrote:

I don't have a Mac, but I tried using iTunes. During the update, the screen froze on the black screen with the Apple logo, and my computer showed an error. The phone became completely unusable; only a service center could revive it. Regarding Wi-Fi or mobile internet, I tried both, and I also tried a VPN, but nothing worked.

If your iPhone won't turn on or is black /frozen / stuck

If your iPhone won't turn on or the screen is black - Apple Support

Further—

or on line  https://getsupport.apple.com/

Outside the USA—Contact Apple for support and service by phone

See a list of Apple phone numbers around the world.

Contact Apple Support - Apple Support 

Sednout wrote:

Greetings! I haven't been able to upgrade to any iOS version for two or three months now.

I download version 26.2 and, as usual, I get an error saying it is temporarily unavailable.

I've tried everything to install the version, and if I try to install it via a computer, an error appears during the update process and the phone turns into a brick!

tried updating how...?

if you are plugged into the Mac(?) you can try Finder >Settings and uncheck Bonjour and relaunch thee Finder or restart and try again...

if WIFI — try updating via Cellular and compare your results.