WordPress url length problem after update

I used wordpress 5.5.3 after I updated to lastest version (5.6.2) I have problem

I have post name slug in Thai which uses UTF-8 character. Many of them encode into super long in ASCII e.g. ???????????????????????????????-8-?????????????????

I’ve changed the type of “post_name” using phpMyAdmin to VARCHAR(1500) and collation to utf8_unicode_ci.

In .htaccess I edited

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

In Formatting.php I edited

$title = utf8_uri_encode( $title, 1500 );

However, in my WordPress backend editor, the above post name is still automatically cut to ?????????????????????? when I try to save the URL.

I don’t know where the problem is, I don’t use a plugin about permalink

What wrong? How to fix?

Thank you