ardour5 hangs at startup

[Christoph]

ardour5 hangs before a window is didplayed.
Ubuntu 19.10
ardour 1:5.12.0-3

Terminal:

~ ardour5
WARNING: Your system has a limit for maximum amount of locked memory!
         This might cause Ardour to run out of memory before your system runs
         out of memory. You can view the memory limit with 'ulimit -l', and it
         is normally controlled by /etc/security/limits.conf

bind txt domain [gtk2_ardour5] to /usr/share/ardour5/locale
Ardour5.12.0 (kompiliert mit Version 1:5.12.0-3 und GCC Version7.3.0)
ardour: [INFO]: Ihre Systemkonfiguration beschränkt Ardour auf nur 1048576 offene Dateien
ardour: [INFO]: Lade Systemkonfigurationsdatei /etc/ardour5/system_config
ardour: [INFO]: CPU vendor: AuthenticAMD
ardour: [INFO]: AVX-capable processor
ardour: [INFO]: CPU brand: AMD Ryzen 5 2600 Six-Core Processor
ardour: [INFO]: Using SSE optimized routines
ardour: [INFO]: lade voreingestellte UI-Konfigurationsdatei /etc/ardour5/default_ui_config
Gtk-Message: 13:56:44.181: Failed to load module "appmenu-gtk-module"
Farbe shuttle bg nicht gefunden
ardour: [INFO]: Lade Farbdatei /usr/share/ardour5/themes/dark-ardour.colors

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: ardour 1:5.12.0-3
ProcVersionSignature: Ubuntu 5.3.0-19.20-generic 5.3.1
Uname: Linux 5.3.0-19-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu Nov 7 13:50:30 2019
InstallationDate: Installed on 2019-10-10 (28 days ago)
InstallationMedia: Ubuntu 19.10 "Eoan Ermine" - Beta amd64 (20190926.1)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/usr/bin/zsh
SourcePackage: ardour
UpgradeStatus: No upgrade log present (probably fresh install)

[Christoph (ch-l)]

`strace ardour5` output attached shows an endless loop.

[Erich Eickmeyer (eeickmeyer)]

System is not set-up properly for audio memory limits. This requires Ubuntu Studio Controls to be run. See https://help.ubuntu.com/community/UbuntuStudio/UbuntuStudioControls for more information.

Since this is basically a support request, it is not a valid bug in a bug tracker.