This seems to be working now, the error is a wee misleading. The code was correct. The URL was incorrect and was changed to (or leave blank):

const url = "sharedprod.braincloudservers.com"; ... brainclouds2s.request(global.s2sContext, { service: "group", operation: "SYS_CREATE_GROUP", data: groupData, }); })

You can bypass the peer dependencies by adding --legacy-peer-deps flag to your npm install. After modifying package.json, then use npm-install-peers to install the rest of peer dependencies.