I think that most tyre/steering chains now have "alignment benchs/tables" - that sort of thing should be able to check camber, though a few years ago, my local one did not seem to have worked out what was needed to check the castor!
These rear bonded bushes do end up distorted in some cases and the material torn in others, I got the LHS one replaced under the 3 year warranty on my wife's August 2015 VW Polo 1.2TSI, when changing the tyres to "winter" at the start of last winter, I spotted that the RHS rear mounting bush looked a bit distorted - as in the centre alloy bush had separated from the rubber material - so I replaced these bushes on both sides a few days ago, the hole in the rubber on the RHS is now oval with an "air gap" at each end, so that bush would be allowing quite a bit of "extra" movement - but no sign of uneven wear on the removed winter tyres - and I do measure them at 3 points after swopping tyres/wheels.
Next idea might be to check the track rods as the inner swivel joints can end up wearing and having a bit of free movement, I had that on a 2002 VW Polo 1.4 16V at around 90K miles, it had been reported as an advisory at the MOT, so I just replaced both track rods and maybe even both TREs. Why I'm suggesting this is, if there is some slack in these track rods, the steering geometry will be free to move about.