i started a thread about the same thing last week. my wifes new bike is boost, mine is non boost and the spare wheel set is non boost. Front wheel is easy.
Rear – emergency only (ie on holiday in the alps or something) i think space the disk, and put 3mm spacers on each side. the cassette is then 3mm too far inboard. in an emergency limit screws and live with terrible chain line. the only ‘proper bodge’ i can see which doesn’t involve relacing the wheel (which isn’t going to happen) is to somehow space the cassette out 3mm. 3mm spacer on the back of the cassette and some kind of extended lockring perhaps. machining up a whole new ‘spaced out’ freehub body is possible but completely over the top for an emergency only solution.
