Cannot log into backend after 'referenceindex:update'

Question

I wanted to update my TYPO3 installation from 9.5.1 to 10.4.9.

This page says to execute php ./typo3/sysext/core/bin/typo3 referenceindex:update on the shell. I did that and got this exception:

Error in GnuTLS initialization: Failed to acquire random data.

Uncaught TYPO3 Exception An exception occurred in driver: php_network_getaddresses: getaddrinfo failed: Name or service not known
thrown in file /is/htdocs/XXX/typo3/typo3-9.5.1/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php
in line 112

When I try to log back into the backend I now get these errors in the browser console:

require-d5051a72d474f75e61b6d2ad78818898.js:1 GET http://XXX/typo3/TYPO3/CMS/Backend/Login.js net::ERR_ABORTED 404 (Not Found)
Uncaught Error: Script error for "TYPO3/CMS/Backend/Login"
http://requirejs.org/docs/errors.html#scripterror
    at makeError (require-d5051a72d474f75e61b6d2ad78818898.js:1)
    at HTMLScriptElement.onScriptError (require-d5051a72d474f75e61b6d2ad78818898.js:1)
require-d5051a72d474f75e61b6d2ad78818898.js:1 GET http://XXX/typo3/TYPO3/CMS/Backend/UserPassLogin.js net::ERR_ABORTED 404 (Not Found)
Uncaught Error: Script error for "TYPO3/CMS/Backend/UserPassLogin"
http://requirejs.org/docs/errors.html#scripterror
    at makeError (require-d5051a72d474f75e61b6d2ad78818898.js:1)
    at HTMLScriptElement.onScriptError (require-d5051a72d474f75e61b6d2ad78818898.js:1)
GET http://XXX/typo3/TYPO3/CMS/Rsaauth/RsaEncryptionModule.js net::ERR_ABORTED 404 (Not Found)
Uncaught Error: Script error for "TYPO3/CMS/Rsaauth/RsaEncryptionModule"
http://requirejs.org/docs/errors.html#scripterror
    at makeError (require-d5051a72d474f75e61b6d2ad78818898.js:1)
    at HTMLScriptElement.onScriptError (require-d5051a72d474f75e61b6d2ad78818898.js:1)

The installation is hosted on a Host Europe webspace.

Configuration is:

• Operating system: Unix
• PHP version: 7.2.34-he.0
• PHP CGI detected: No
• DB Version: MySQL 5.7.30