Make no mistake, even the J1 was a designed-for-Android platform (delayed 6 months to make libhybris, remember?). Jolla was going to use the ST-Ericsson Snowball(?) platform which was basically the last platform that sipped a Linux adaptation and not only an Android one, but it was cancelled. This J2 is more than likely going to be on a platform targeted at Android. I think maaaybe Qualcomm has one with official non-Android Linux support (which might be just as buggy), but never heard of it for MediaTek.
With that said, there are of course worse and better choices of hardware still. Jolla will of course have made sensible choices as far as they could. And honestly a lot of what big G is doing for driver interfaces and mainlining is actually for the better - just challenging to keep up with at times.