Your site is performing updates over FTP due to file ownership.

Check out the article here: https://www.ads-software.com/support/article/changing-file-permissions/

You have to set the user and group to values of your server environment, of course. Nobody knows them here. But the above mentioned article shows the direction.

Thanks for your reply. I feel like I’ve followed the direction in that article, but I’m obviously missing something.

Changing the group of everything in html and opening file perms a bit restored the ability to upload media, so partial success there:

chown -R :www-data html
find html/ -type d -exec chmod 775 {} \;
find html/ -type f -exec chmod 664 {} \;

Those were at the recommendation of the above-linked article. Site health continues to give the same error, though, and I still can’t update plugins, etc.

Update: Late in the article referenced, it mentions su-php. This is a fresh Digital Ocean droplet, so I assumed su-php would not be running, however this seems to indicate that it is:

ps aux | grep php-fpm
root      155150  0.0  0.0   8156   656 pts/0    S+   17:41   0:00 grep --color=auto php-fpm

That being the case, I changed ownership of all files in html back to root (which seems like a bad idea to me, but anyway). Still no change.

Ok, figured this out. The issue was with the user not being assigned to the correct group. What wasn’t making sense to me was that WordPress runs as the server (www-data on Ubuntu), so I didn’t think the user should own the files. The problem was that the user needed to be added to that group:

sudo usermod -aG www-data $USER
sudo chown -R www-data:www-data html

(Ran under the user, not as root).