I have Second Life installed on its own SSD and located; on a Windows 11 system, at "J:/Program Files/SecondLifeViewer". I keep all non-system applications off of the boot drive where APPDATA is located.  I have attempted multiple times to use the suggested method of '.\SLSetup.exe –installto J:/Program Files/SecondLifeViewer' and unfortunately it is still installing to 'AppData\Local\SecondLifeViewer'.  In addition, I have added both Single and Double quotes to the "–installto" folder, all to know avail.
This is my first time reporting an issue so, if you need anything additional please reach out.
Thank you for your assistance in getting past this issue.