I highly recommend Harmony University online!
They have tons of courses in performance, singing, coaching, private lessons as a separate item ($50) barbershop history, quarteting, arranging, etc
They also have shows and coaching under glass, which I originally thought was useless to me, as I am not a director, but as I watched someone else get coached, I started hearing things I had never understood before.
For example, they had top singers come in and change their voice to be nasally, or tense tongue, or having a spot in their range that was going awry, and then apprentice coaches tried to help them solve their issues, and in the end, a Master Coach would give his feedback, and there were 6 different Master coaches, all with slightly different styles.
You can watch in your own time for a few months afterwards as well, or you can participate in the class and ask questions when it is live.
You save $20 if you sign up now, ($99), and you get all the shows, all the courses, all the community connections, (coaches gave out their emails and asked for people to ask them questions). Private lessons are extra. T
In addition, they usually have a la carte options later on that are cheaper.