I don’t know if you have solved this problem. I just registered segmentfault yesterday, so I didn't see your problem earlier. I encountered similar problems to you in the past. You have not successfully changed the file root directory of apache - changing the root directory of apache requires changing two files, one is /etc/apache2/sites-available/000-default.conf (you changed this), and the other One is /etc/apache2/apache2.conf (you missed this one).
What you need to do is change what I call the second configuration file:
vim /etc/apache2/apache2.conf
Then press i to enter edit mode, scroll down (remember it should be very far back...) to find

<Directory /var/www/>
       Options Indexes FollowSymLinks
       AllowOverride None
       Require all granted
</Directory>

Change it to

<Directory /var/www/wordpress>
       Options Indexes FollowSymLinks
       AllowOverride All  //改成All是为了开启Rewrite模式
       Require all granted
</Directory>

That should be enough, I hope it helps.

1. Are directory permissions allocated appropriately?

2. Look at the screenshot, you can enter the homepage, but other pages are 404, it may be that rewrite is not turned on, the root directory of the website may need an .htaccess file to configure rewirte

In fact, your domain name directory configuration should not put wordpress under ../html/, but under /var/www/, and then configure the root directory in site-avaliable to /var/www/wordpress, like this If so, there will be no problem with the style not coming out