It is usually possible to skip wifi connection during setup, but they have been making it harder.
I'm sure others will jump in with the disadvantages of not registering and the advantages of registering.
If avoiding updates is your main goal, there are some options.
It might be that you can jailbreak. The box should have the serial number, which can be used with the information in the thread
https://www.mobileread.com/forums/sh...d.php?t=338766
to determine manufacture data and precice model. Then a good guess can be made whether a jailbreak can be done.
With jailbreak, updates can be blocked and it is possible to "fake register".
As a last resort, updates can be blocked on any kindle by reducing free space to less than 200 megabytes.