Phaedra Rinn

I recognize this is an old thread - but there are no newer ones open and I figure having one thread instead of many is best. I'm trying to do the same thing as you OP, getting a raspberry pi DSI display working on a rockpi 4b+. I tried to adapt Radxa's DTS in a similar way you did from Armbian's Base DTS, and seeing what definitions changed and I came up with this non working DTS:
 
 
Which gives the following DMESG error, very similar to yours:
`[ 21.477004] rpi-ts-dsi ff960000.dsi.0: failed to attach dsi to host: -517 [ 21.477086] mipi-dsi ff960000.dsi.0: deferred probe pending: (reason unknown)`  
You'll note various differences between our DTS, like panel_in instead of panel_in_dsi, and mipi_dsi instead of mipi_dsi1. I based these off looking at the base DTS in Armbian kernel 6.18.32, but also on this project I found recently that brings support for 7 and 10 inch Osoyoo brand of DSI panels to the RockPi 4b+. I think that's really promising and will help with bringing DTS support to the raspberry pi panel (and others that are compatible). I recommend you look into it. I will continue iterating and update this thread with results if any.
 
I don't think OP was pinning the problem on Armbian. OP was asking how to configure a custom DTS to work with the hardware they have. This is the community support forum, which is the correct place for this kind of discussion.