I've updated the INDI libraries and drivers on Slackbuilds.org (SBo).
INDI Library is a collection of programs designed to control
astronomical equipment, such as, cameras, telescopes, etc. In addition
to the drivers and modules provided in the main INDI distribution,
there are a number of third party drivers available. For more
information on INDI refer to https://www.indilib.org/

Stellarium (https://slackbuilds.org/repository/15.0/academic/stellarium/)
has INDI support to directly control telescope positioning.  Kstars,
included with Slackware's KDE, Provides INDI support via the built-in
EKOS client. Besides telescope control, numerous devices are supported,
including CCD cameras. Why pay good money for proprietary and expensive 
telescope GOTO and astrophotography software when perfectly functional
opensource alternatives exist?

To get Kstars/Ekos operational in Slackware (or whatever other Linux
distribution. I won't judge.), you will need to recompile Kstars. INDI
is a compile-time dependency; therefore, the Kstars package included
with Slackware does not include INDI functionality.

Feedback is appreciated, for bugs and improvements, via sbo@linuxgalaxy.org

For Slackware (What? Are you still using that *other* distro?), follow this
build order.  Everything needed is included either in the main Slackware
tree or on SBo.  Note that the SBo buildscripts for libindi-libraries and
libindi-drivers are optional. These include the third party drivers not
present in the main libindi build.  This list is also the recommended build
and installation order.  If you do not know what drivers you need (!!),
install everything.

Dependency	Needed by
--------------------------
libev		libindi
libnova		libindi
wcslib		stellarsolver
stellarsolver	Kstars/EKOS

[optional for third-pary drivers]
gpsd		GPS devices, libindi-libraries, -drivers
libdc1394	firewire/IEE1994 cameras, libindi-libraries, -drivers
libftdi1	FTDI's UART/FIFO chips, libindi-libraries, -drivers

INDI
----
libindi			any INDI client
libindi-libraries	libindi-drivers (optional)
libindi-drivers		(optional)

Kstars INDI Client
------------------
Kstars in Slackware-15 is a bit too old. Grab the Kstars source from
Slackware current or from https://invent.kde.org/education/kstars/-/branches
(version 3.6.0 as of this post). On Slackware current, this should be enough
to recompile Kstars so that INDI gets incorporated. Example is for
Slackware-current downloaded to '/data/ and assuming KDE is installed.

# su -
# cd /data/slackware[64]-current/source/kde/kde
# ./kde.SlackBuild applications-extra:kstars
# upgradepkg --reinstall /tmp/kstars-3.6.0-[x86_64,i586]-1.txz

To build kstars-3.6.0 on Slackware-15, you can use these buildscript files.
Apologies to native Catalan speakers:
see https://invent.kde.org/education/kstars/-/issues/186

Files are also located https://www.linuxgalaxy.org/files/sbo-testing/ 

-----------------
kstars.SlackBuild
-----------------

#!/bin/bash

# Slackware build script for kstars
# 
# Copyright 2022 Edward Koenig, Vancouver, WA, USA
# All rights reserved.
#
# Redistribution and use of this script, with or without modification, is
# permitted provided that the following conditions are met:
#
# 1. Redistributions of this script must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ''AS IS'' AND ANY EXPRESS OR IMPLIED
# WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
# EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
# OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
# OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
# ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

# initial test 16-AUG-2022

cd $(dirname $0) ; CWD=$(pwd)

PRGNAM=kstars
VERSION=${VERSION:-3.6.0}
BUILD=${BUILD:-1}
TAG=${TAG:-_SBo}
PKGTYPE=${PKGTYPE:-tgz}

if [ -z "$ARCH" ]; then
  case "$( uname -m )" in
    i?86) ARCH=i586 ;;
    arm*) ARCH=arm ;;
       *) ARCH=$( uname -m ) ;;
  esac
fi

# If the variable PRINT_PACKAGE_NAME is set, then this script will report what
# the name of the created package would be, and then exit. This information
# could be useful to other scripts.
if [ ! -z "${PRINT_PACKAGE_NAME}" ]; then
  echo "$PRGNAM-$VERSION-$ARCH-$BUILD$TAG.$PKGTYPE"
  exit 0
fi

TMP=${TMP:-/tmp/SBo}
PKG=$TMP/package-$PRGNAM
OUTPUT=${OUTPUT:-/tmp}

if [ "$ARCH" = "i586" ]; then
  SLKCFLAGS="-O2 -march=i586 -mtune=i686"
  LIBDIRSUFFIX=""
elif [ "$ARCH" = "i686" ]; then
  SLKCFLAGS="-O2 -march=i686 -mtune=i686"
  LIBDIRSUFFIX=""
elif [ "$ARCH" = "x86_64" ]; then
  SLKCFLAGS="-O2 -fPIC"
  LIBDIRSUFFIX="64"
else
  SLKCFLAGS="-O2"
  LIBDIRSUFFIX=""
fi

set -e

rm -rf $PKG
mkdir -p $TMP $PKG $OUTPUT
cd $TMP
rm -rf $PRGNAM-$VERSION
tar -xvf $CWD/$PRGNAM-$VERSION.tar.xz
cd $PRGNAM-$VERSION
chown -R root:root .
find -L . \
 \( -perm 777 -o -perm 775 -o -perm 750 -o -perm 711 -o -perm 555 \
  -o -perm 511 \) -exec chmod 755 {} \; -o \
 \( -perm 666 -o -perm 664 -o -perm 640 -o -perm 600 -o -perm 444 \
  -o -perm 440 -o -perm 400 \) -exec chmod 644 {} \;

# remove Catalan translation from ./po because kdoctools too old (15.0)
# https://invent.kde.org/education/kstars/-/issues/186
# Not needed for Slackware-current
rm -rf po/ca
rm -rf po/ca@valencia

mkdir -p build
cd build
  cmake -DCMAKE_INSTALL_PREFIX=/usr \
    -DCMAKE_CXX_FLAGS:STRING="$SLKCFLAGS" \
    -DCMAKE_C_FLAGS:STRING="$SLKCFLAGS" \
    -DCMAKE_BUILD_TYPE="release" \
    ..
  make
  make install DESTDIR=$PKG
cd -

find $PKG -print0 | xargs -0 file | grep -e "executable" -e "shared object" | grep ELF \
  | cut -f 1 -d : | xargs strip --strip-unneeded 2> /dev/null || true

mkdir -p $PKG/usr/doc/$PRGNAM-$VERSION
cp -a AUTHORS ChangeLog INSTALL TODO README.* LICENSES $PKG/usr/doc/$PRGNAM-$VERSION
cat $CWD/$PRGNAM.SlackBuild > $PKG/usr/doc/$PRGNAM-$VERSION/$PRGNAM.SlackBuild

mkdir -p $PKG/install
cat $CWD/slack-desc > $PKG/install/slack-desc
cat $CWD/doinst.sh > $PKG/install/doinst.sh

cd $PKG
/sbin/makepkg -l y -c n $OUTPUT/$PRGNAM-$VERSION-$ARCH-$BUILD$TAG.$PKGTYPE

-----------------
doinst.sh
-----------------
if [ -x /usr/bin/update-desktop-database ]; then
  /usr/bin/update-desktop-database /usr/share/applications >/dev/null 2>&1
fi
-----------------
slack-desc
-----------------
# HOW TO EDIT THIS FILE:
# The "handy ruler" below makes it easier to edit a package description. Line
# up the first '|' above the ':' following the base package name, and the '|' on
# the right side marks the last column you can put a character in. You must make
# exactly 11 lines for the formatting to be correct. It's also customary to
# leave one space after the ':'.

      |-----handy-ruler------------------------------------------------------|
kstars: kstars (a desktop planetarium)
kstars:
kstars: KStars is free, open source, cross-platform Astronomy Software.
kstars: It provides an accurate graphical simulation of the night sky, from
kstars: any location on Earth, at any date and time. The display includes up
kstars: to 100 million stars, 13,000 deep-sky objects, all 8 planets, the Sun
kstars: and Moon, and thousands of comets, asteroids, supernovae, and
kstars: satellites.
kstars:
kstars: Homepage: https://edu.kde.org/kstars
kstars:
-------------------