CrossUO is developed by a team that worked on Orion. It's an open source suite that includes a launcher, an updater and a client, to play UO on the platform of your choice and that works with many eras of the game and with almost any shard!!!
There's also an assistant Razor-like in development that is not released yet. The multilingal team is ready to answer your questions and read your feedback if there's anything with the suite.
To follow the project:
Website: https://crossuo.com
Discord: https://discord.gg/FhNvsb6
Github: https://github.com/crossuo/
Be a part of a new old school adventure! The immortal Ultima Online is now available on mac and linux!