If you never used DynDoLod then you should check out this guide:
DynDoLod's HD trees offer a great lighting cause the lod trees are using normal maps too.
The transition isn't as perfect as Hybrid Trees offer.
But it is much better than the usual billboards. And it is very performance friendly. And a good performance is the goal of this mod.
You need to grab DynDoLod 3 alpha first. You will get the instructions of necessary additional downloads there. Also see this guide.
And after installing everything you have to use TexGen.
You can also use my TexGen.ini settings if you want.
You find the TexGen_SSE.ini in the "DynDOLOD\Edit Scripts\DynDOLOD" of your DynDoLod installation.
These are my settings:

Then you have to start TexGen.
And the following settings turned out to work pretty good:

You need to copy the folders in the TexGen_Output into your Skyrim SE data folder.
In the next step you have to start DynDoLod, switch to the advanced settings and enable the "Ultra" box.
Then you move to treesIn the mesh and reference rules in the upper section of the window and set the lod levels to billboard4

And then you press OK.
Install the generated lod into your Skyrim SE data folder and you have a nice, fast lod.
24 comments
It sounds like you are running an incorrect version of SKSE for the game version you are using. Post on the DynDOLOD support forums for assistance.
And 3D Lods will come soon enough.
Check https://www.nexusmods.com/skyrimspecialedition/mods/56907 ( Happy Little Trees Add-On - DynDOLOD 3 ):
Official DynDOLOD 3D hybrid LOD models for "Hasppy Little Trees". Built using the latest DynDOLOD 3 tools and uploaded with approval from T4gtr34um3r to provide LOD to augment his mod while he continues development.
I'll do this only for testing purposes.
I ran DynDoLod and TexGen a lot of times the last days to find good values.
It's just unchecked on picture by mistake, T4 already explained why it was unchecked.
Might be better to update the pic to avoid confusion though @T4gtr34um3r
edit: It doesn't seem to be this mod causing the issue because reverting to a prior version resolves my CTD
But I'll focus on the lod again. Though this is are the last steps of this mod.