Which free public vpn service do you recommend for Ubuntu?

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Anyone using a free public online vpn service on Ubuntu?
Which existing free public vpn service do you recommend?

Proxies don't encrypt all ports and setting up my own vpn server isn't the
goal at all.

The goal is to point my saucy salamander desktop to an existing free public
vpn service on an ad-hoc basic, whenever I want, where the vpn service
maintains the vpn server, not me.

Googling for "free public vpn service", I find hits for:
* 7 Completely Free VPN Services To Protect Your Privacy *
* 5 Great Free VPN Services Compared: Which Is Fastest? *
* TOP 10 FREE VPN (VIRTUAL PRIVATE NETWORK) SERVICES *
etc.

But almost all of these are Windows clients.

If you're using a free public online vpn service on Ubuntu,  
which existing free public vpn service do you recommend?

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