It looks like .host domains in China now require real-name registration too.
My 233.host domain was blocked from resolving. I did not notice that at first; I just could not work out why the site would not load, so I switched to shiyu.dev. I had already planned to use that domain and had simply been putting it off. When 233.host ran into trouble, it became a good reason to make the change.
The migration mostly meant changing stored data, but there were more places to update than I expected. The site URL can be changed directly in the admin panel. Everything else has to be handled in the database. Running SQL updates is the most practical way to replace the old domain with the new one in bulk.
First, links inside posts:
UPDATE `typecho_contents` SET `text` = REPLACE(`text`,'旧域名地址','新域名地址');
Next, URLs in comments:
UPDATE typecho_comments SET url = REPLACE(url,'旧域名地址','新域名地址');
Then the homepage header image:
UPDATE typecho_fields SET str_value = REPLACE(str_value,'旧域名地址','新域名地址');
Replace the Chinese placeholders in each statement with the old and new domain names. After those three updates, the main work was done.
West.cn handled it quite quickly.