With the recent release of Pro 2.5 I thought I would be able to easily update the SDK extensions in Visual Studio 2017 to continue development. Right? Wrong!
Here some pitfalls I found you may wish to avoid, read on if you'd like to avoid wasting time climbing in and out of the traps. Installation was relatively fresh install of VS2017 used exclusively for two Esri projects under Pro 2.3 and no other SDKs.
It started when I downloaded the Pro 2.5 SDK. The SDK is no longer an automatic installer/updater but works through updating the extension in VS (official Esri instructions). However this didn't work at all - after downloading the update and showing update pending "Click Close to dismiss the dialog and exit Visual Studio." I closed it... for step 6 "The VSIX Installer dialog will appear." and nothing happened. No hidden processes running, just a silent desktop.
This is a known problem with VS2017. No matter what I did including esoteric hints from StackExchange et al about closing the IDE in a certain way/procedure, first putting on my wizard robe and hat, making sure VS was fully updated, etc it would not start the update process, and when the update was chosen again, it would faithfully tell me it was about to update the SDK then troll me by doing nothing at all.
(as a side-issue Windows 10 also did not update automatically to install the required .NET framework 4.8 and had to be done manually)
Eventually I found some hope in a Repair of VS. After spending several hours(!) reinstalling 446 updates it wiped the previous Pro SDKs and gave me a vanilla VS. Yay
Finally, I was able to choose the SDK and when VS closed, the VISX installer dialog appeared.
On reflection I should probably have just completely ignored all the documentation and advice from MS and done an end-run around VS by directly running the proapp-sdk-utilities.vsix and proapp-sdk-templates.vsix that came with the SDK download from Esri. Not tested, but I suspect it would be faster than dealing with the above bargewaffle. Yes I am salty Microsoft, I want those hours of my life back..