Mozilla does provide flatback and official Flatpak for thunderbird, but they are always behind release and they usually stick for long time at old versions.

I don't want also to have to check for updates and do them manually on my linux machine. so I wrote this to do automate the process

1. Create the auto-update script: ~/.local/bin/update-thunderbird

#!/bin/bash
set -euo pipefail

LOG="${HOME}/.local/log/thunderbird-update.log"
mkdir -p "$(dirname "$LOG")"

log() { echo "[$(date +'%Y-%m-%d %H:%M:%S')] $*" | tee -a "$LOG"; }
error() { echo "[$(date +'%Y-%m-%d %H:%M:%S')] ERROR: $*" >&2 | tee -a "$LOG"; exit 1; }

log "Starting Thunderbird update check..."

# --- 1. Get candidate version from API ---
CANDIDATE_VERSION=$(curl -fsS "https://product-details.mozilla.org/1.0/thunderbird_versions.json" \
  | jq -r '.LATEST_THUNDERBIRD_VERSION // empty')
if [[ -z "$CANDIDATE_VERSION" ]]; then
  error "Failed to fetch version from Mozilla API"
fi
log "Candidate version (API): $CANDIDATE_VERSION"

# --- 2. Validate .deb exists for candidate; if not, fall back to latest published ---
validate_version() {
  local v="$1"
  local url="https://archive.mozilla.org/pub/thunderbird/releases/${v}/linux-x86_64/en-US/thunderbird-${v}.deb"
  if curl -fsSI "$url" | head -n1 | grep -q "200"; then
    echo "$v"
    return 0
  fi
  return 1
}

VERSION=""
if validate_version "$CANDIDATE_VERSION"; then
  VERSION="$CANDIDATE_VERSION"
  log "Using candidate version: $VERSION"
else
  log "Binary for $CANDIDATE_VERSION not yet available. Falling back to latest published..."
  VERSION=$(curl -fsS "https://archive.mozilla.org/pub/thunderbird/releases/" \
            | grep -oE 'href="[0-9]+\.[0-9]+(\.[0-9]+)?/"' \
            | sed 's|href="||; s|/"||' \
            | grep -v -i 'esr' \
            | sort -V \
            | tail -n1)
  if [[ -z "$VERSION" ]]; then
    error "No non-ESR versions found"
  fi
  log "Fallback version: $VERSION"
  validate_version "$VERSION" || error "Even fallback version $VERSION has no .deb"
fi

# --- 3. Get installed version ---
INSTALLED_VERSION=""
if dpkg -l thunderbird &>/dev/null; then
  INSTALLED_VERSION=$(dpkg-query -f '${Version}' -W thunderbird 2>/dev/null \
                        | sed 's/.*://' \
                        | cut -d'-' -f1 \
                        | sed 's/esr.*//')
  log "Installed version: $INSTALLED_VERSION"
else
  log "Thunderbird not installed"
fi

# --- 4. Compare versions and exit early if already up-to-date ---
if [[ -n "$INSTALLED_VERSION" && "$INSTALLED_VERSION" == "$VERSION" ]]; then
  log "Already up-to-date (installed: $INSTALLED_VERSION, latest: $VERSION)."
  exit 0
fi

# --- 5. Download & install ---
DEB_FILE="/tmp/thunderbird-${VERSION}.deb"
DEB_URL="https://archive.mozilla.org/pub/thunderbird/releases/${VERSION}/linux-x86_64/en-US/thunderbird-${VERSION}.deb"

log "Downloading $DEB_URL"
curl -fsSL "$DEB_URL" -o "$DEB_FILE"

log "Installing..."
sudo dpkg -i "$DEB_FILE" || sudo apt-get -f install -y

log "Thunderbird updated to $VERSION"
rm -f "$DEB_FILE"

# Optional: desktop notification
if command -v notify-send >/dev/null; then
  notify-send "Thunderbird Updated" "v$VERSION installed" --icon=mail-unread
fi

log "Done."

2. Make it executable & test

chmod +x ~/.local/bin/update-thunderbird
mkdir -p ~/.local/log

Test dry-run (comment out dpkg/apt lines first if cautious)

~/.local/bin/update-thunderbird

3. Automate with systemd timer (I prefer over cron as more reliable) Create ~/.config/systemd/user/thunderbird-update.timer

[Unit]
Description=Check for Thunderbird updates weekly

[Timer]
OnCalendar=weekly
Persistent=true
RandomizedDelaySec=3600

[Install]
WantedBy=timers.target

And ~/.config/systemd/user/thunderbird-update.service

[Unit]
Description=Update Thunderbird to latest release
After=network-online.target

[Service]
Type=oneshot
ExecStart=%h/.local/bin/update-thunderbird
Environment=HOME=%h

Then enable:

systemctl --user daemon-reload
systemctl --user enable --now thunderbird-update.timer

This Runs weekly, survives reboots and send logs to ~/.local/log/thunderbird-update.log.

Or as an alternative we can use this one-liner for quick manual check

Add to ~/.bashrc or ~/.bash_aliases:

alias tb-update='VERSION=$(curl -s https://product-details.mozilla.org/1.0/thunderbird_versions.json | jq -r .LATEST_THUNDERBIRD_VERSION) && echo "Latest: $VERSION" && wget -qO /tmp/tb.deb "https://download.mozilla.org/?product=thunderbird-$VERSION&os=linux64&lang=en-US" && sudo dpkg -i /tmp/tb.deb || sudo apt --fix-broken install -y && rm -f /tmp/tb.deb'

Then simply run

tb-update