Whoops, somehow I missed them when dropping the files in the folder. Here's the Debug log (I have no idea why it is so big since it's from 1 generation). The other log is in the attachments.
Yes, since the generation with xLODgen was taking a lot of time (and space) and terrain lod swap occours only in winter, I decided to cut off the other seasons (just trees do swap during the 4 seasons, but they are generated by DynDOLOD). If is this that's causing trouble, I am more than happy to generate just the winter season with DynDOLOD so that they can match, or maybe I'm dumb and should only have generated lod for Tamriel and Wyrmstooth in the first place, since every other worldspace has no configuration file in the seasons folder. I have no idea. Only Tamriel world space had the [Seasons] identifier in advanced mode window, but I should have seen also Wyrmstooth since it is configured to have 4 seasons. To summarize: I selected all world spaces in advanced mode in DynDOLOD but only Tamriel had the [Seasons] identifier. Perhaps, I could try to generate seasonal lod just for Tamriel with xLODGen and DynDOLOD leaving every else unthicked and see what happens?
However, I can't explain why Solstheim does switch season.
Also, one other thing I noted was that modifing object LOD distance and terrain LOD distance multiplier only works in Tamriel. In particular, object LOD distance seems to be stuck to 0 in other world spaces (Markarth and Solstheim for example) and increasing it in the MCM does nothing.
DynDOLOD_SSE_log.txt