By skyforbes 
People running business-critical applications that still depend on .NET Framework 3.5 can fix this with a special standalone installer. It's a Dot Net 3.5 "VNext" that is currently in Preview status. See Photo.
Link to Microsoft announcment and VNext download for those on Canary channel now (Nov 2025) or who find this when it hits release.
Dot Net 3.5 will no longer Autoload. If any legacy code still uses it, you will get a notification and the app will no longer run. This crash will happen in 10.0.27900.0 or higher.
There is no way as far as I know to know when this will happen to you, or to pre-load this until each system is updated. Then you may see crashes.
I know my accounting systems at work and about 10K game servers dating back 20 years will need this just for one game, even though devs thought they were on Dot Net 9. Nope, they forgot one DLL.