Hello,
pondering...

I could set up a VPN tunnel (*) between my home server and my android phone, instead of browsing the internet directly (from my phone that is).

however, both the mobile broadband connection and my home ethernet connection are from the same ISP!

in that case, would there even be any benefit (security-, privacy- or otherwise) from doing so?

...

additional info:
- the mobile broadband is unlimited (capped, but unlimited)
- on the phone, i am using a firewall (AFWall+) and a non-google dns server. also at home i do not use the dns servers provided by my ISP. i use opennic servers for both.

(*) not sure i'm getting the terminology right; hope you get my meaning.

I don't see how there could be any benefits privacy or securitywise if you had a secure connection to your home compared to using your mobile internet. It would only mean that you're redirecting traffic and you'd probably (maybe insignificantly) have lower throughput. I don't think it would make any difference even if you you had different ISPs, really.

I would use VPN especially if I connected to a Public WiFi or to some other WiFi connection that I don't trust. But in your case, the traffic would eventually travel the same way (from a security/privacy perspective).

If you want security/privacy, then I'd suggest using paid VPN that all sorts of companies offer or you could use tools such as Tor browser, for instance.

On the other hand, I admit that I don't know much about the lower-layer protocols being used on the mobile internet, but I doubt anyone would normally be able to sniff it too easily.

I use a vpn on android when I am on public (free) wifi. But it is a a "normal" commercial vpn, not just a tunnel back to my home. I agree the benefits are likely to be minimal in your case - unless you also tunnel out of your home network.
I found the vpn is always active, and chews the hell out of the battery, so I now fire it up when I need it.

thanks for these insights.
it is as i thought.

the only reason i can still think of is that google would be listening in less, somehow, if i use the vpn.
since i already use non-google dns on the phone, it would have to happen in some more hidden layers of the android OS - any ideas on that?

I think I've changed my mind. Use it.
We all reckon there isn't enough privacy out there, so whatever you (we) can do to improve the situation has to be a benefit.

I don't know what vpn client you are going to use, but as I said, the proprietary client I use (PIA) is a pig on the battery if I leave it active. No reason to do so really, but it something I wasn't aware of before I started.

as i said, i would only use my own server, not a commercial service.

vpn seems to be baked into my OS, i see an option in the settings menu, so no client required i guess. i'd probably also have to revise AFWall+ settings.

i'll wait for some more comments on the possible benefits of this, the inner workings of android & sending data to google...

Android will wend your data to Google regardless. At first one would think that the location would be obscured by using a VPN at home (showing only the home location) but since the entire OS is owned by Google they could easily have it send your true IP address anyhow.
If you're using Android you've already sold all your life to Google like the rest of us. Either do without a "smart phone" or give google your life -- they are the only options.