Hi
I recently installed TeXmacs 1.99.9 on Linux Mint 19.1 as a systemwide installation in /opt/TeXmacs. I initially defined
TEXMACS_PATH and added TEXMACS_PATH/bin to the PATH variable. Initially texmacs could not find guile2.0 but that was fixed after defining GUILE_LOAD_PATH. At this point if I type texmacs & in at a terminal, I received the following error message in the terminal

TeXmacs] Installation problem: please send a bug report.
TeXmacs] The initialization file init-texmacs.scm could not be found.
TeXmacs] Please check the values of the environment variables
TeXmacs] TEXMACS_PATH and GUILE_LOAD_PATH. init-texmacs.scm should
TeXmacs] be readable and in the directory $TEXMACS_PATH/progs
TeXmacs] or in the directory $GUILE_LOAD_PATH
TeXmacs]
Throwing guile could not be found
-------------------------------------------------
Error message:
  guile could not be found
System information:
  TeXmacs version  : 1.99.9
  Built by         : magix
  Building date    : Wed Feb  6 18:53:48 CET 2019
  Operating system : linux-gnu
  Vendor           : pc
  Processor        : @CONFIG_HOST_CPU@
  Crash date       : Fri  5 Apr 17:10:52 AEST 2019

TeXmacs server not yet started
Backtrace of C++ stack:
  texmacs.bin() [0xf65105]
  texmacs.bin() [0x57a578]
  texmacs.bin() [0xb8de1c]
  texmacs.bin() [0x414703]
  /lib/x86_64-linux-gnu/libc.so.6 : __libc_start_main() + 0xe7
  texmacs.bin() [0x40e4b9]

-------------------------------------------------
terminate called after throwing an instance of 'string'
 
I figured that this  was a permissions problem associated with me having the file ownership as root:root for the items in /opt/TeXmacs. Using sudo texmacs & at the terminal prompt allowed the init-texmacs.scm file to be found. TeXmacs now appears to be running under my username and saves to my home directory.

I have never experienced having to run software installed under /opt with root:root ownership using sudo privileges in any other software package so I thought it was worth reporting in case there is a fix which makes this unnecessary. Also other packages I use which use guile seem to be able to find the libraries without defining the GUILE_LOAD_PATH environment variable (usually from /usr/lib  not usr/share/guile?).  I had used a symlink from /usr/bin to /opt/TeXmacs/bin/texmacs but this did not work until the above environment variables had all been defined in /etc/environment and reloaded.