Dear all,
I just compiled TeXmacs 1.99.7 on Ubuntu 18.04. As is well known, the only build requirement not provided by Ubuntu versions later than 16.04 is guile-1.8-dev. This package cannot be installed in Ubuntu 18.04, since it depends on libreadline6-dev, which has been superseded by libreadline-dev (which provides version 7).
As it turns out, it is straightforward to compile Guile 1.8.8 in Ubuntu 18.04 and afterwards compile TeXmacs. Therefore, I do not understand what is the big deal with providing a TeXmacs package in Ubuntu.
In order to encourage further testing and (hopefully) the comeback of TeXmacs to the Ubuntu repos, here is what I did:
$ tar xvfJ rootfs.tar.xz
$ proot -S rootfs bash
In the following # denotes the root shell inside PRoot
# export PATH=$PATH:/sbin:/usr/sbin:/usr/local/sbin
# apt update
# apt install wget git
These are Guile's build dependencies
# apt install --no-install-recommends autoconf automake debhelper dh-autoreconf flex libgmp-dev libltdl-dev libncurses5-dev libreadline-dev libtool texinfo
# tar xzvf guile-1.8.8.tar.gz
# cd guile-1.8.8
# ./configure --disable-dependency-tracking --enable-error-on-warning=no
# make
# make install
These are TeXmacs' build dependencies
# apt install --no-install-recommends build-essential autotools-dev cdbs debhelper ghostscript imagemagick ispell libfreetype6-dev libimlib2-dev libjpeg-progs libltdl-dev libqt4-dev librsvg2-bin libtiff-tools libx11-dev libxt-dev netpbm quilt r-base-core x11proto-core-dev xfig
# cd GNUTeXmacs
# ./configure
# make
Voilà!