I use a simple and sane solution: Forms. Unfortunately, that's not yet supported by the Matrix specification, but the XMPP standard has an XEP for that. No separate software required for login.
I hope the Matrix standard will also incorporate that idea at some point. They've already added so many ideas from XMPP, I'm confident that one would be especially great to also add there. :)
We also need interoperability between the two, they have very similar goals and we should decrease fracturing for IM. Just imagine how large the combined user-base could be!