regarding safari: https://caniuse.com/#search=worker
workers are supported, so the dist versions not using shared workers can run there already.
2 missing items on the webkit side:
1) adding support for shared workers (they dropped the development on those, but recently put it into "inRadar" again. So there is hope.
2) adding support for JS modules inside the worker scope. missing in FF as well. not too bad, since it is good enough in case 1 browser can do it (chrome) so that the dev mode can run there. the dist versions will run in FF, safari & chrome, since webpack is replacing all import statements, so that there are no real JS modules.
to fully support mobile, neo.mjs still needs to support touch events (similar to hammer js). on the todo list.