Whilst I'm not a fan of the name, I'm more discouraged that it needs to specify a fx at all which suggests that the library hasn't come up with a generic solution for all fx's but rather a library of quirks to abstract over a limited set of fx's.
Since it only has hard-coded support for 3 frameworks, there's no benefit to using magic strings, it would be preferable to use a typed API like:
XSM.useReact({ ... })
Where you can provide fx-specific options for each fx it supports. It also hides all the config options available behind a generic API which you have to dive into the impl [1] to see what options are available and what args each config option supports. Everyone would be far better off bringing all config options to the API Surface area, you could easily type-check all options in TypeScript which ensures correct usage of the API and let you know of any additions/removal or breaking changes.
[1] https://github.com/peterluhub/xsm/blob/master/xsm.js