Sadly I have to install Pulseaudio on both system as Firefox audio refused to work

Are you using the firefox-esr package from the Devuan repositories? That version is compiled with the --enable-alsa option and so will provide audio without PA.

XDG_RUNTIME_DIR is set automatically by systemd in Debian buster: https://www.freedesktop.org/software/sy … stemd.html

~/.xsessionrc should work fine but /etc/environment (or a file under /etc/environment.d/) would probably be better.

EDIT: For my Alpine Linux system I use this stanza in ~/.profile:

if test -z "${XDG_RUNTIME_DIR}"; then
   export XDG_RUNTIME_DIR="/tmp/$(id -u)-runtime-dir"
   if ! test -d "${XDG_RUNTIME_DIR}"; then
      mkdir "${XDG_RUNTIME_DIR}"
      chmod 0700 "${XDG_RUNTIME_DIR}"
   fi
fi

Have two Devuan systems; one ASCII and the new toy Beowolf.  They are largely configured the same way, basic window manager; Openbox and not much else, (the way I like my systems).  I do indulge in some flatpak based packages, one of them being Spotify.  This works without much of an issue in ASCII but not so well under Beowolf. I stumble on the "Pulseaudio connection refused issue"  Sadly I have to install Pulseaudio on both system as Firefox audio refused to work.
I notice the ASCII had a particular environment variable set for my X session: XDG_RUNTIME_DIR.  This was absent on Beowolf. I also attempted to determine where on ASCII this was set as it is configure before X is run.  (Please note the ASCII X session is start manually via "startx"),  I have not yet found the where this variable is set.  I use SLIM manager on the Beowolf system - not sure if this is the difference.  Most external documentation suggest various ways of setting XDG_RUNTIME_DIR, however they all assume that systemd is being used.

What I ended up doing, and this was based on what /etc/X11/Xsession script was doing, is as follows:

I created a file .xsessionrc in my user home directory containing:
export XDG_RUNTIME_DIR="/run/user/$(id -u)"

This seemed to be the only non system wide place where this was accepted and set.  Now flatpak spotify works in Beowolf using Pusaudio.

Questions:  Is this variable XDG_RUNTIME_DIR supposed to be set? If so where is this set (in both ASCII and Beowolf)

I am not sure I place the config in the correct place, however, for now it work

Regards
Buggycode