Upgrading from 5.8.2 to 5.9 says fully upgraded

Try a manual update: https://www.ads-software.com/support/article/updating-wordpress/#manual-update

I just want to use the gutenberg editor.

The block editor (aka Gutenberg editor) came with WordPress 5.0 and should already be included in 5.8.2. If you’re not seeing it, then, very likely, a plugin you’ve installed has disabled it… and simply updating WordPress will not change that. (That’s not to say don’t update your WordPress site though ?? )

Ah, wordpress.com!

Due to the differences between the various site hosting plans offered at wordpress.com and the self-hosted and self-installed version of WordPress supported here, you should probably ask WordPress.com support instead: https://wordpress.com/support/help-support-options/

In such cases, the best strategy is trying the manual update.