Likely this is a result of linking Qt5 statically, but not libX11/libxcb:
(gdb) bt
[#0](/bitcoin-bitcoin/0/) 0x0000555555a530ed in QXcbKeyboard::updateVModMapping() ()
[#1](/bitcoin-bitcoin/1/) 0x0000555555a535c8 in QXcbKeyboard::QXcbKeyboard(QXcbConnection*) ()
[#2](/bitcoin-bitcoin/2/) 0x0000555555a6845d in QXcbConnection::QXcbConnection(QXcbNativeInterface*, bool, char const*) ()
[#3](/bitcoin-bitcoin/3/) 0x0000555555a523ef in QXcbIntegration::QXcbIntegration(QStringList const&, int&, char**) ()
[#4](/bitcoin-bitcoin/4/) 0x0000555555a5149b in QXcbIntegrationPlugin::create(QString const&, QStringList const&, int&, char**) ()
[#5](/bitcoin-bitcoin/5/) 0x0000555556111b43 in QPlatformIntegrationFactory::create(QString const&, QStringList const&, int&, char**, QString const&) ()
[#6](/bitcoin-bitcoin/6/) 0x0000555555f04486 in QGuiApplicationPrivate::createPlatformIntegration() ()
[#7](/bitcoin-bitcoin/7/) 0x0000555555f052c5 in QGuiApplicationPrivate::createEventDispatcher() ()
[#8](/bitcoin-bitcoin/8/) 0x000055555637c010 in QCoreApplication::init() ()
[#9](/bitcoin-bitcoin/9/) 0x000055555637c085 in QCoreApplication::QCoreApplication(QCoreApplicationPrivate&) ()
[#10](/bitcoin-bitcoin/10/) 0x0000555555f05c39 in QGuiApplication::QGuiApplication(QGuiApplicationPrivate&) ()
[#11](/bitcoin-bitcoin/11/) 0x0000555555bca162 in QApplication::QApplication(int&, char**, int) ()
[#12](/bitcoin-bitcoin/12/) 0x00005555556adb52 in BitcoinApplication::BitcoinApplication (this=0x7fffffffd930, argc=<optimized out>, argv=<optimized out>) at qt/bitcoin.cpp:306
[#13](/bitcoin-bitcoin/13/) 0x00005555556becc6 in main (argc=2, argv=0x7fffffffdd68) at qt/bitcoin.cpp:509
The 32-bit bitcoin-qt, as well as 32 and 64-bit bitcoind and bitcoin-cli work as expected.