ok, same here, using nightly appimage OpenXcom_20200211_bdfd52280_x86-64.AppImage on debian/mint.
As far as I understand -and according to the logfile-, below should be a correct datapath.
It obviously isnĀ“t, otherwise I wouldn't post here
[12-02-2020_23-05-45] [INFO] Platform: Unix-like
[12-02-2020_23-05-45] [INFO] Data folder is: /tmp/.mount_OpenXcMGvONQ/usr/share//openxcom/
[12-02-2020_23-05-45] [INFO] Data search is:
[12-02-2020_23-05-45] [INFO] - /home/jan/.local/share/openxcom/
ls -l /home/jan/.local/share/openxcom/UFO
total 2696
-rwxrwxrwx 1 jan jan 14965 Jul 10 1994 BASE.EXE
-rwxrwxrwx 1 jan jan 254556 Jan 11 1994 DOS4GW.EXE
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 editor
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 GEODATA
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 GEOGRAPH
-rwxrwxrwx 1 jan jan 1169 Mar 23 1994 GO.COM
-rwxrwxrwx 1 jan jan 98727 May 22 1994 INSTALL.EXE
-rwxrwxrwx 1 jan jan 102380 Mar 14 1994 INTRO.EXE
drwxrwxrwx 2 jan jan 12288 Dec 19 2018 MAPS
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 MISSDAT
drwxrwxr-x 2 jan jan 4096 Feb 12 22:08 mods
-rwxrwxrwx 1 jan jan 83648 May 22 1994 MPSCOPY.EXE
-rwxrwxrwx 1 jan jan 1388544 Aug 23 2001 msvbvm60.dll
-rwxrwxrwx 1 jan jan 2120 Apr 4 2005 readme.txt
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 ROUTES
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 RUNEXE
-rwxrwxrwx 1 jan jan 26647 Mar 14 1994 SETUP.EXE
-rwxrwxrwx 1 jan jan 12441 Jul 10 1994 SOLDIER.EXE
-rwxrwxrwx 1 jan jan 967 Nov 17 2003 SOLDIER.PIF
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 SOUND
-rwxrwxrwx 1 jan jan 10 Jul 21 2003 SOUND.CFG
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 TERRAIN
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 UFO2EXE
-rwxrwxrwx 1 jan jan 779 Mar 25 1994 UFOCHEAT.COM
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 UFOEXE
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 UFOGRAPH
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 UFOINTRO
drwxrwxrwx 2 jan jan 4096 Dec 19 2018 UNITS