This script allows you to extract and register a Vivaldi Linux deb or rpm package with your Desktop Environment using a unique keyword, to assist with multiple side-by-side "installs".

register-vivaldi.sh

#!/bin/sh -eu
a=off
if [ "x${1:-}" = "x-n" ] && [ -n "${2:-}" ]; then
  n="${2#vivaldi-}"
  c="Vivaldi-$n"
  a=on
  echo "Using the name: vivaldi-$n"
  shift 2
fi
if [ -n "${1:-}" ]; then
  if echo "$1" | grep -qE "vivaldi-(stable|snapshot)[_-]([0-9]+\.){3}[0-9]+-[0-9]+[_\.][a-z0-9_]+\.(rpm|deb)" && [ -e "$1" ]; then
    v="${1##*/}"
  else
    echo "$1 is not a Vivaldi package" >&2
    exit 1
  fi
else
 echo -e "Supply the name of the Vivaldi .deb or .rpm package you wish to register like so:\n\n   $0 vivaldi-stable-6.1.3035.84-1.x86_64.rpm\n" >&2
 exit 1
fi
cd "$(dirname "$1")"
[ "$a" = on ] && d="${v%.*}-$n" || d="${v%.*}"
[ -d "$d" ] && rm -r "$d"
mkdir "$d"
cd "$d"
echo "Extracting: $v" >&2
if [ "${v##*.}" = deb ]; then
  ar p "../$v" data.tar.xz | tar Jx ./opt ./usr/share/applications --strip 3
else
  tail -c+"$(grep -Fabom1 7zXZ "../$v" | cut -d: -f1)" "../$v" | xz -d | cpio --quiet -id ./opt\* ./usr/share/applications\*
  mv opt/vivaldi*/* .
  mv usr/share/applications .
  rm -r opt usr
fi
w="$(find . -maxdepth 1 -type f \( -name vivaldi -o -name vivaldi-snapshot \))"
x="$(echo applications/*.desktop)"
chmod 755 $x
if [ "$a" = on ]; then
  f="vivaldi-$n"
  sed -i "s,/${w#*/}/,/$f/,g;/^exec -a/s,\"\$@\", --user-data-dir=\"\${XDG_CONFIG_HOME:-\$HOME/.config}/$f\" --class=\"$c\" \"\$@\"," $w
  sed -i "s,^Icon=${w#*/},Icon=$f,;0,/^Name=/s,^Name=.*,Name=Vivaldi ($n),;/^StartupNotify/ i StartupWMClass=$c" $x
  if [ -x update-ffmpeg ]; then
    sed -i "s,/${w#*/}/,/$f/,g" update-ffmpeg
  fi
else
  f="${w#*/}"
fi
cat <<REGISTER> register
#!/bin/sh -eu
update_dbs () {
  touch -c "\${XDG_DATA_HOME:-\$HOME/.local/share}/icons/hicolor" 2>/dev/null ||:
  if command -v gtk-update-icon-cache >/dev/null 2>&1; then
    gtk-update-icon-cache -tq "\${XDG_DATA_HOME:-\$HOME/.local/share}/icons/hicolor" 2>/dev/null ||:
  fi
  if command -v update-desktop-database >/dev/null 2>&1; then
    update-desktop-database -q "\${XDG_DATA_HOME:-\$HOME/.local/share}/applications" 2>/dev/null ||:
  fi
}
if [ "x\${1:-}" = "x-d" ]; then
  rm -fv "\${XDG_DATA_HOME:-\$HOME/.local/share}/applications/$f.desktop" "\${XDG_DATA_HOME:-\$HOME/.local/share}/icons/hicolor"/*/apps/$f.png
  if [ -h "\$HOME/bin/$f" ]; then
    rm -v "\$HOME/bin/$f"
  elif [ -h "\${XDG_DATA_HOME:-\$HOME/.local/share}/../bin/$f" ]; then
    rm -v "\$(cd "\${XDG_DATA_HOME:-\$HOME/.local/share}/../bin"; pwd)/$f"
  fi
  update_dbs
  exit
fi
cd "\${0%/*}"
for p in product_logo_*.png; do
  s="\$(echo \$p | grep -o '[0-9]\+')"
  l="\${XDG_DATA_HOME:-\$HOME/.local/share}/icons/hicolor/\${s}x\$s/apps"
  mkdir -p "\$l"
  ln -vfs "\$PWD/\$p" "\$l/$f.png"
done
sed -i "s,^Exec=.*vivaldi\(-stable\|-snapshot\)* ,Exec=\$PWD/${w#*/} ," $x
mkdir -p "\${XDG_DATA_HOME:-\$HOME/.local/share}/applications"
ln -vfs "\$PWD/$x" "\${XDG_DATA_HOME:-\$HOME/.local/share}/applications/$f.desktop"
if [ -d "\$HOME/bin" ]; then
  ln -vfs "\$PWD/${w#*/}" "\$HOME/bin/$f"
elif [ -d "\${XDG_DATA_HOME:-\$HOME/.local/share}/../bin" ]; then
  ln -vfs "\$PWD/${w#*/}" "\$(cd "\${XDG_DATA_HOME:-\$HOME/.local/share}/../bin"; pwd)/$f"
fi
update_dbs
REGISTER
chmod 755 "register"
printf "Creating symlinks:\n\n" >&2
cd - >/dev/null
if [ ! -e "$f" ] || [ -h "$f" ]; then
  ln -fsT "$d" "$f"
  d="$f"
fi
"$d/register"
cat <<HELP

        NOTE: You may need to re-login before $f shows up!

                                  ***

        To remove symlinks and de-register $f issue:

  '$PWD/$d/register' -d

HELP

Running it with -n followed by your chosed name/keyword/stream (e.g. -n alt) and then the Vivaldi package would result in something like the following:

$ ./register-vivaldi.sh -n alt vivaldi-stable-6.1.3035.100-1.x86_64.rpm
Using the name: vivaldi-alt
Extracting: vivaldi-stable-6.1.3035.100-1.x86_64.rpm
Creating symlinks:

'/home/ruario/.local/share/icons/hicolor/128x128/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_128.png'
'/home/ruario/.local/share/icons/hicolor/16x16/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_16.png'
'/home/ruario/.local/share/icons/hicolor/22x22/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_22.png'
'/home/ruario/.local/share/icons/hicolor/24x24/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_24.png'
'/home/ruario/.local/share/icons/hicolor/256x256/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_256.png'
'/home/ruario/.local/share/icons/hicolor/32x32/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_32.png'
'/home/ruario/.local/share/icons/hicolor/48x48/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_48.png'
'/home/ruario/.local/share/icons/hicolor/64x64/apps/vivaldi-alt.png' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/product_logo_64.png'
'/home/ruario/.local/share/applications/vivaldi-alt.desktop' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/applications/vivaldi-stable.desktop'
'/home/ruario/bin/vivaldi-alt' -> '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/vivaldi'

        NOTE: You may need to re-login before vivaldi-alt shows up!

                                  ***

        To remove symlinks and de-register vivaldi-alt issue:

  '/home/ruario/Downloads/vivaldi-stable-6.1.3035.100-1.x86_64-alt/register' -d

This version of Vivaldi would now be available from Gnome, KDE Plasma, Xfce, etc. menus and launcher as "Vivaldi (alt)". It will use its own settings and will not be touched when you upgrade other streams such as stable or snapshot.

Alternatively you can skip -n keyword and the script will just register the build as is, without changing the stream.

It does not really matter so much if you choose an rpm or deb package, since an install is not taking place and thus neither the rpm nor dpkg commands need to be present.

It may be slightly more reliable to use the rpm because the deb package needs ar for extraction and some distros do not install this by default. While the rpm package does rely on cpio as part of its extraction, this is (almost always) preinstalled.

In either case, if you found that ar or cpio were not present, just install the "binutils" or "cpio" packages (respectively) via your package manager, before attempting to run the script again.