after renaming skse64_loader.exe to SkyrimSELauncher.exe, skse (64) would attempt to load but fail reporting a memory allocation error. Vanilla Skyrim would then load. Had to recompile source code for skse64 myself from the github page https://github.com/ianpatt/skse64/commit/4a1e1219578890fb8cfb077daf08b386855ec62f using a Windows VM and VisualStudio community edition, with the 2015 compiler. Hopefully these new binaries get added to the SKSE official website soon. To get SkyUI to load, I had to add the line *SkyUI_SE.esp to /path/to/steam/library/steamapps/compatdata/489830/pfx/drive_c/users/steamuser/Local\ Settings/Application\ Data/Skyrim\ Special\ Edition/Plugins.txt