url rewrite broken after update (3.3 -> 3.5)

Hi,

I updated my contao installation from 3.3 to 3.5 and now the URL rewriting is broken.
"rewrite URLs" is checked and "URL suffix" is empty, thus a valid URL is p.ex. www.domain.com/contact

The .htaccess.default contains:
# If you do not want to use an URL suffix at all, you have to add a third
# line to prevent URLs that point to folders from being rewritten (see #4031).

#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteRule .* index.php [L]

I have to following behaviour:

If I do NOT use these rules, I can see the start page with styles, etc. ok, but the links are broken. P.ex. www.domain.com/contact leads to 404 Not Found.

If I do use these rules. I can navigate (p.ex to contact) but all styles, downloads, etc is broken and leads to "Page not found" Contao error page.
Additionally, I can not login anymore. System log reports: No active page for page ID "contao"

What is wrong here??

Knut

The problem was in the .htaccess (good guess). The documentation should be improved...

https://github.com/contao/core/issues/7930