When I run bitcoin-qt it does not properly start up and hangs in futex():

The last calls shown in strace are:
```
futex(0x7f3f7bfd77e4, FUTEX_WAKE_PRIVATE, 2147483647) = 0
futex(0x7f3f7d812c60, FUTEX_WAIT, 65792, NULL
```

gdb shows:

```
(gdb) bt
#0  syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1  0x00007ffff5e26d2f in __cxa_guard_acquire () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#2  0x00007ffff7e06dcc in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#3  0x00007ffff7e0b706 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#4  0x00007ffff7e2af21 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#5  0x00007ffff7e32080 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#6  0x00007ffff7df1c67 in QSslCertificate::QSslCertificate(QByteArray const&, QSsl::EncodingFormat) ()                                                                                        
   from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#7  0x00007ffff7e07fe6 in ?? () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5
#8  0x00007ffff7dfb09d in QSslConfiguration::defaultConfiguration() () from /usr/lib/x86_64-linux-gnu/libQt5Network.so.5                                                                      
#9  0x000055555564841f in main () at qt/bitcoin.cpp:579
#10 0x00007ffff5a49b17 in __libc_start_main (main=0x555555648380 <main>, argc=1, argv=0x7fffffffdcc8, init=<optimized out>, fini=<optimized out>,                                             
    rtld_fini=<optimized out>, stack_end=0x7fffffffdcb8) at ../csu/libc-start.c:310
#11 0x0000555555657dca in _start () at /usr/include/c++/8/ext/new_allocator.h:116
```

I understand that this might also be a problem in Qt rather than bitcoin-qt.
But other Qt applications do not show this problem. So I'd be happy to get any hint to debug this further.

Thanks!

{
#ifdef ENABLE_WALLET
    gArgs.AddArg("-allowselfsignedrootcertificates", strprintf("Allow self signed root certificates (default: %u)", DEFAULT_SELFSIGNED_ROOTCERTS), true, OptionsCategory::GUI);
#endif
    gArgs.AddArg("-choosedatadir", strprintf("Choose data directory on startup (default: %u)", DEFAULT_CHOOSE_DATADIR), false, OptionsCategory::GUI);
    gArgs.AddArg("-lang=<lang>", "Set language, for example \"de_DE\" (default: system locale)", false, OptionsCategory::GUI);
    gArgs.AddArg("-min", "Start minimized", false, OptionsCategory::GUI);
    gArgs.AddArg("-resetguisettings", "Reset all settings changed in the GUI", false, OptionsCategory::GUI);
    gArgs.AddArg("-rootcertificates=<file>", "Set SSL root certificates for payment request (default: -system-)", false, OptionsCategory::GUI);
    gArgs.AddArg("-splash", strprintf("Show splash screen on startup (default: %u)", DEFAULT_SPLASHSCREEN), false, OptionsCategory::GUI);
    gArgs.AddArg("-uiplatform", strprintf("Select platform to customize UI for (one of windows, macosx, other; default: %s)", BitcoinGUI::DEFAULT_UIPLATFORM), true, OptionsCategory::GUI);
}
#ifndef BITCOIN_QT_TEST
int main(int argc, char *argv[])
{
    SetupEnvironment();
    std::unique_ptr<interfaces::Node> node = interfaces::MakeNode();
    
    
    Q_INIT_RESOURCE(bitcoin);
    Q_INIT_RESOURCE(bitcoin_locale);
    BitcoinApplication app(*node, argc, argv);
#if QT_VERSION > 0x050100
    
    QApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
#endif
#if QT_VERSION >= 0x050600