How do we ensure that Skyrim SE doesn't update so we don't have to reinstall SKSE?

Solution 1:

Two things you can do:

Firsty, you can just launch Steam in offline mode so there's no way for anything to update

Secondly you can try this:

• Go to where Steam is installed (if you have multiple install spots on separate HDDs you need to go to the drive where Skyrim is installed)
• Under steam\steamapps you'll see a bunch of .acf files, open appmanifest_489830.acf (this is the Skyrim .acf file) in notepad (right click .acf > open with > notepad)
• Find AutoUpdateBehavior and change it to -1 and make sure BytestoDownload is set to 0
• Save and close the notepad document, right click the same .acf (appmanifest_489830.acf) > properties > read-only > press OK

This should fix this issue. If not, may have to use Steam offline.

If in future you want to update the game, revert all these settings, default values for AutoUpdateBehavior is 0 and BytesToDownload is also 0 and make sure you deselect read-only.