The advantage of the built in crypto library is, that it is completely self contained, with no external dependencies.
Your suggested library seems to have 8 external dependencies: https://git.duniter.org/libs/g1lib.js/-/blob/main/package.json#L41. Several of them have other dependencies.
Only 1 package has some info about 3rd party auditing. I don’t see, why a crypto library needs node-fetch as a dependency, which in turn have plenty more dependencies … node-fetch is for networking and imo has nothing to offer for a crypto library.
If it is “compiled” and minified, how big is it the whole stuff?
I personally wouldn’t touch it.