in terminal:
ubuntu-support-status --show-unsupported
ubuntu-support-status --show-all | less

* * *

Surveillance Self-Defense
Tips, Tools and How-tos for Safer Online Communications
https://ssd.eff.org/

Instant messaging
https://en.wikipedia.org/wiki/Comparison_of_instant_messaging_clients
https://www.securemessagingapps.com/

Privacy Tools
https://www.privacytools.io/ -> https://privacytoolsio.github.io/privacytools.io/

VPN
https://protonmail.com/blog/best-vpn-service/

ProtonVPN - not free but claims to be the most secure one...
https://twitter.com/ProtonVPN
https://facebook.com/ProtonVPN
https://reddit.com/r/ProtonVPN
https://protonvpn.com/
https://protonvpn.com/support/
https://protonmail.com/blog/best-vpn-service/

Unseen VPN
https://www.unseen.online/ - claims to be free and no spying...
https://download.unseen.is/ - in the VPN section you can download an
alpha version of VPN software
https://for-god-and-country.blog/2016/07/29/announcing-the-unseen-p2p-vpn/
http://cryto.net/~joepie91/blog/2014/04/19/why-you-should-stay-away-from-unseen.is/
- also interesting reading....

SSHuttle - wise man's VPN
https://wiki.itcollege.ee/index.php/Sshuttle
https://github.com/apenwarr/sshuttle
https://sshuttle.readthedocs.io/
http://packages.ubuntu.com/search?keywords=sshuttle&searchon=names&suite=all&section=all
http://teohm.com/blog/using-sshuttle-in-daily-work/
https://www.unixmen.com/sshuttle-poor-mans-vpn-ssh/

Preventing attacks
https://www.grepular.com/Protecting_a_Laptop_from_Simple_and_Sophisticated_Attacks
http://www.datamation.com/security/protecting-your-ubuntu-desktop-1.html
http://www.tldp.org/HOWTO/Secure-Programs-HOWTO/cross-site-malicious-content.html
http://resources.infosecinstitute.com/how-to-prevent-cross-site-scripting-attacks/
https://www.owasp.org/index.php/XSS_%28Cross_Site_Scripting%29_Prevention_Cheat_Sheet

* * *
http://enos.itcollege.ee/~edmund/materials/ssh.txt

https://wiki.ubuntu.com/BasicSecurity
https://www.ubuntu.com/usn/ - Ubuntu security notices
https://people.canonical.com/~ubuntu-security/cve/
https://www.cvedetails.com/vulnerability-list/vendor_id-51/Ubuntu.html
https://help.ubuntu.com/lts/serverguide/security.html
https://insights.ubuntu.com/2016/12/08/ubuntu-16-04-lts-security-a-comprehensive-overview/
https://www.slideshare.net/dustinkirkland/ubuntu-1604-lts-security-features
http://www.itsecurity.com/features/ubuntu-secure-install-resource/
https://www.thefanclub.co.za/how-to/how-secure-ubuntu-1604-lts-server-part-1-basics
https://www.maketecheasier.com/secure-newly-installed-ubuntu/
http://www.psychocats.net/ubuntu/security
http://www.techrepublic.com/article/how-to-harden-ubuntu-server-16-04-security-in-five-steps/
https://sites.google.com/site/easylinuxtipsproject/security
https://www.digitalocean.com/community/tutorials/how-to-monitor-your-system-security-with-osquery-on-ubuntu-16-04
http://www.datamation.com/open-source/hardening-ubuntu-security.html
https://tecadmin.net/install-security-updates-ubuntu-debian/