"Both monism and many worlds can be avoided, but only when one either changes the formalism of quantum mechanics—typically in ways that are in conflict with Einstein’s theory of special relativity—or if one understands quantum mechanics not as a theory about nature but as a theory about knowledge: a humanities concept rather than science."

Tut-tut. There's nothing "humanities rather than science" about the understanding that QM is 'just' probability theory

https://arxiv.org/abs/quant-ph/0601158 https://terrytao.wordpress.com/tag/noncommutative-probabilit... https://arxiv.org/abs/math-ph/0002049 https://ncatlab.org/nlab/show/quantum+probability

applied to mechanics (and interpreted sensibly, as it is in any 'neo-Copenhagen' or 'pragmatist' interpretation). Grandiose and/or bizarre 'psiontology' is easily avoided.