Hey! I recently had a go at writing my first integration! I hope to add a remote entity to it still to send CEC commands to both inputs and outputs, but it seems to be working well for my 4x4 matrix
Link: https://github.com/taysuus/hass-orei_matrix
I also made a quick feature for the tile card to show a select dropdown for the source, this helps my dashboard with this integration https://github.com/taysuus/source-select-feature
If anyone else has these matrices, I’d love your feedback! 
I have just watched a great YouTube video on these. By a channel called Cameron grey. ( He does some really cool home automation and AV /networking stuff…super interesting…ANYWAY, this kinda system is what I’m looking at for my new house, so a script like this will come in super handy! I’ll feedback in the future once it’s all set up and I’ve given it a good. Thanks! 
Thanks for this! I have just bought an OREI 8x8 matrix and will test this integration out.
Did you manage to look into the CEC commands to send to inputs as that would be really handy to automate commands in HA.