Honda is pretty decent. Suzuki doesn't sell service data but the info you need is readily available from Clymer. Royal Enfield is fantastic for service data.
Most Japanese bikes are very user friendly. Even the newer ones aren't terrible to work on. If you want the easiest mix of technology and ease of repair shoot for a Japanese motorcycles before 2014-ish.
I was considering triumph as my first bike but after reading this its a hard pass.
To your knowledge are there any brands known for being DIY friendly on current models (read being able to provide/sell offline service manuals)?