disable core dump:

/etc/security/limits.conf
* hard core 0
* soft core 0

/etc/sysctl.d/9999-disable-core-dump.conf
fs.suid_dumpable=0
kernel.core_pattern=|/bin/false
---
sudo sysctl -p /etc/sysctl.d/9999-disable-core-dump.conf

disable tracker (run under user):
systemctl --user mask tracker-extract-3.service tracker-miner-fs-3.service tracker-miner-rss-3.service tracker-writeback-3.service tracker-xdg-portal-3.service tracker-miner-fs-control-3.service
tracker3 reset -s -r

remove exim4:
apt-get -y remove --purge exim*

apple avahi:
sudo systemctl stop avahi-daemon
sudo systemctl disable avahi-daemon
sudo systemctl stop cups-browsed 
sudo systemctl disable cups-browsed
sudo systemctl stop cups
sudo systemctl disable cups

chrome - disable discovery
chrome://flags/#device-discovery-notifications
mkdir -p /etc/opt/chrome/policies/managed
echo '{ "EnableMediaRouter": false }' > /etc/opt/chrome/policies/managed/disable_mediarouter.json
mkdir -p /etc/opt/chrome/policies/managed
echo '{ "EnableMediaRouter": false }' > /etc/opt/chrome/policies/managed/disable_mediarouter.json

UI
https://github.com/velitasali/gtktitlebar
https://extensions.gnome.org/extension/1160/dash-to-panel/
disable hot corners

gsettings set org.gnome.desktop.interface color-scheme prefer-dark

Alt-tab
in gnome keyboard settings, set shortcut for Switch Windows to Alt+Tab