That's exactly the message i got.

On Fri, Nov 2, 2018, 14:10 Sitaram Chamarty <sitaramc@gmail.com wrote:

> On Fri, Nov 02, 2018 at 08:39:28AM +0100, Kalin KOZHUHAROV wrote:
> > On Fri, Nov 2, 2018 at 8:26 AM Laszlo KERTESZ <laszlo.kertesz@gmail.com>
> wrote:
> > > The current FDroid build (version 0.0.20181031) is broken. The Gui
> starts but it states "Unknown userspace Go version" and the tunnel
> activation action results in an error.
> > >
> > Hmm... just installed (1st time) and started it, seems fine (haven't
> > configured it yet).
> > What is your configuration?
> >
> > Here: stock (no root) Android-8.1.0 (3.18.71-perf-gd0e0d1a kernel) on
> > XT1905 phone.
>
> I can confirm the problem, though the error I see is different:
>
>     Error bringing up tunnel: No implementation found for java.lang.String
>     com.wireguard.android.backend.GoBackend.wgVersion() (tried
> Java_com_wireguard_android...
>
> (I'm sorry I have n o idea how to expand that message to its
> full text, whatever it may have been)
>