This has been really annoying. Trying to discover why my VPS could not get through to wordpress.org. During installation of the WP script on Debian 10, it was unable to fetch the script from wordpress.org as it could not access WP. I then downloaded the script from wordpress.org separately, and uploaded it with FileZilla. Everything worked exactly as it should except I was unable to install plugins or auto update them through the Dashboard.
I was at least able to manually upload my All in One Migration Extension Plugin from my backup, as well as the All in One Migration plugin from WordPress.org Website. Then when I tried to import a backup WordPress Website, the All in One Migration plugin forced me to update the Extension Plugin. Strangely enough after the update, the plugin changed into auto update. I now have only one auto update plugin. My Website is unable to reach wordpress.org, however is performing very well.
I must have spent hours and hours trying to figure out why my Debian 10 Buzzer cannot reach WordPress.org. WordPress Dashboard had me believe that the problem was on my side. It offered a very long list of suggestions, including Debian permissions. I checked through them all. Finally I discovered an online discussion at WordPress that indicates that WordPress does not really support IPv6. WordPress expects the whole world to do a Nat64 so IPv6 can be IPv4 compatible.
https://meta.trac.wordpress.org/ticket/3090
Personally I’ve come to the conclusion auto plugins and auto installation are overrated. Everything else works excellent, seamless and fast. And I feel protected by Cloudflare. I installed the Cloudflare plugin in WP today, and the promise is that the Cloudflare plugin will provide for faster and more secure operation of WordPress. So far my Website on the VPS with IPv6 has been performing seamlessly and blazingly fast!
For any one who is interested in setting up their IPv6 with Cloudflare I found a great tutorial at Hostinger:
https://www.hostinger.com/tutorials/how-to-setup-cloudflare-for-wordpress