TYPO3 And IOS: Can't Open The Page

My situation:
I have 10 typo3-websites running on two servers:

• First Server (apache with php 5.6.32):
  • typo3 versions: 6.2.3, 6.2.4 and 6.2.14
• Second Server (apache with php 7.0.26):
  • typo3 versions: 7.6.14 and 8.7.1.

• I'm not able to open the page on an iPhone or iPad with osx 10.x or above. I tested it on safari, chrome and firefox, but I get always an error like: "[browser] can't open the page (...) because the server unexpectedly dropped the connection. (...)"

• On a mac (osx 10), I get the error only in safari 11.0.2, but not in firefox or chrome.

• I can open the pages without any problems, if I'm logged in at the typo3-backend with the same browser.

• A Wordpress-Page is also running on the second server without any problems.

• I have no problems on windows, android or other linux machines.

I tried the following without success:

• clearing the typo3 cache
• using the default .htaccess
• using an empty .htaccess
• The solutions from this site (german!): http://www.typo3forum.net/discussion/79617/ios-10-3-1-laedt-seite-nicht

Any ideas?

Have you tried to set the header content-length to 0? https://docs.typo3.org/typo3cms/TyposcriptReference/Setup/Config/Index.html#enablecontentlengthheader

Try to set the following lines to your TypoScript

config.enableContentLengthHeader = 0

You say you can open the page if you are logged in that matches the following description:

If the Backend user is logged in, this is disabled. The reason is that the content length header cannot include the length of these objects and the content-length will cut off the length of the document in some browsers.