I'm unable to find any kind of release notes for the TS library of SignalR. There's not even a readme here:
https://github.com/dotnet/aspnetcore/tree/main/src/SignalR/clients/ts

And no links to changelogs here either:
https://www.npmjs.com/package/@microsoft/signalr

I can see the versions numbers go up... no idea what has changed.