Thing is, it does not really matter too much, and logging in over Tailscale to your residential ISP can be super slow! Some ISPs have fast download speeds, but super slow upload speeds. I’ve stayed at quite a lot of hotels and the average internet speeds kinda sucks.
If you’re that paranoid (which after reading the bottom I don’t think you should be), you could setup a hotspot on your server.
SSH is encrypted, by default
You can generate an SSL certificate, install it on the server and install it on your client to encrypt the connection from end-to-end
For SSH, you can use SSH keys rather than passwords, or you could use something like Yubico PAM Auth.
I mean, you can use a Raspberry Pi and a powerbank. The max you can bring on a plane is 27,000 mAh, which should be more than enough if you’re hours away from a constant plugin source. Also, a lot of planes have plugin spots, and you can get a car to plugin adapter on amazon for like $20. I have one and it works fine drawing 65W to my laptop.
Also, I sorta accidentally brought more than 27,000 mAh on a plane from Atlanta to Boston and they didn’t really seem to care all that much lol
You’re thinking about cell service. There has been Wi-Fi on planes for over a decade. T-mobile users and SkyMiles account holders get them on Delta for free (I have both). There are two major satellite providers, Viasat and GoGo. Nobody likes GoGo. Delta (and others) use Viasat. I watched YouTube on my plane ride lol.
To address the second part, if you have a raspberry pi, you can turn it into a ad-hoc WAN to access your content.
Regardless, you can’t expect there to be WiFi everywhere. And even if there was you’d still disconnect from the Airplane WiFi, connect to the airport WiFi, then walk through the airport and connect to more more more. And if you are using signals from cell towers they still have holes in their coverage.