Hi @nirvanascott, in Yousician the tuner is designed to get you in tune to play the song, so if you'd like to use an alternate tuning, just select a song that uses that tuning, and the tuner adapts. If it's a parallel tuning like Eb (or if a song uses a capo), then there will be an option to transpose the song to match standard tuning for you (rather than re-tune yourself).
In the syllabus there's a mission on alternate tunings, which focuses on Dropped-D since that's the most popular one. Otherwise, you can find or upload songs in the Songs section that use an alternate tuning, and the tuner will adapt to whatever you want to play.
Hope that helps!