Support for SermonSpeaker 5.x is in bugfix mode only, the same as it is for Joomla 3.10.
I will not add any new features to this releases.
Please upgrade to SermonSpeaker 6.x and Joomla 4.x, which is better anyway.
Unfortunastely due to the way PreachIt stores the speakers, it's not easy to associate them automatically.
I havent' looked at it for some time but according to a comment I made in the code it stores the speakers as a string into the sermon table. This allows to add multiple speakers to a sermon (which SermonSpeaker doesn't allow) but it makes it almost impossible to use database queries on it.
So you will have to associate them manually. You can do so using the batch functions to assign a speaker to multiple sermons in one go.