Does anyone know where I can find the Hebrew text for the Rambam's letter to Ovadia the Ger online, and a good Hebrew language shiur on it?
The Rambam wrote three letters to Ovadya the Ger. The Hebrew text can be found in Teshuvos HaRambam 42, 345 and (probably the most famous one) 369. These are the only letters to him in the volume (according to the index).
Here is a Hebrew lecture series on them that I found in a search but didn't watch.