[GNC] Workaround issue reports ssh into flatpak on Proxmox container

[G McAlister]

This is to describe a workaround for an issue with reports crashing when 
using x-forwarding over ssh into a flatpak gnucash running in a Proxmox 
lxc container. Yep, weird, I know.

I try to run all my apps in Proxmox lxc containers and access them 
through ssh from my linux workstation. Generally, this works well. For 
gnucash, my distro (opensuse leap 15.5) is deliberately slow to update 
apps and, having followed this list for some time, it is clear that I 
should keep up to date with the latest releases. Looking for the 
simplest way to keep up to date, I settled on flatpak because it's much 
simpler than compiling from source. So, I launched a new lxc container 
on Proxmox using the template 
opensuse-15.6-default_20240910_amd64.tar.xz. In this container, I 
installed flatpak and gnucash (version 5.9). I launched gnucash using 
flatpak run org.gnucash.GnuCash and was able to create accounts, import 
transactions, etc. It was when I came to try a report that gnucash 
crashed. The console messages were:

libEGL warning: DRI3: Screen seems not DRI3 capable
libEGL warning: DRI3: Screen seems not DRI3 capable
MESA: error: ZINK: failed to choose pdev
libEGL warning: egl: failed to create dri2 screen

Googling the MESA error line led me to the flatpak reddit 
(https://www.reddit.com/r/flatpak/comments/wuqqr9/how_do_i_fix_a_flatpak_thats_not_working/) 
and a link in that thread to this 
https://gitlab.com/freedesktop-sdk/freedesktop-sdk/-/wikis/Mesa-git 
which gave a workaround.

The workaround suggested is to install the mesa-git extensions:

flatpak remote-add --user flathub-beta 
|https://flathub.org/beta-repo/flathub-beta.flatpakrepo
flatpak install --user flathub-beta org.freedesktop.Platform.GL.mesa-git

Then run gnucash using this incantation:

FLATPAK_GL_DRIVERS=mesa-git flatpak run org.gnucash.GnuCash

Now the gnucash reports work as expected.