I can launch Olympus, and if I click around in the right places I can actually get Celeste/Everest to launch, but for whatever reason none of the UI shows. I attached a picture, not that there's much to see. The only log file that had anything I could find was AppData\Local\Olympus\log-launcher.txt, which says this:
Olympus Launcher 1.0.0.0
Tried to start C:\Users\kfish\AppData\Roaming\Olympus\main.exe but not found.
Starting up form
Downloader thread running
Wiping C:\Users\kfish\AppData\Roaming\Olympus
System.IO.IOException: The process cannot access the file 'C:\Users\kfish\AppData\Roaming\Olympus' because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
at System.IO.Directory.DeleteHelper(String fullPath, String userPath, Boolean recursive, Boolean throwOnTopLevelDirectoryNotFound, WIN32_FIND_DATA& data)
at System.IO.Directory.Delete(String fullPath, String userPath, Boolean recursive, Boolean checkHost)
at Olympus.OlympusForm.RunDownloader()
Downloading https://dev.azure.com/EverestAPI/Olympus/_apis/build/builds/1774/artifacts?artifactName=windows.main&$format=zip
Downloaded 8087300 bytes
Opening wrapper .zip
Opening dist .zip
Extracting to C:\Users\kfish\AppData\Roaming\Olympus
Done
Starting up C:\Users\kfish\AppData\Roaming\Olympus\main.exe
Unsure what this means, especially since the file it lists definitely does exist, but yeah.
I'm on Windows 11, with whatever version of olympus was on the GameBanana page.

not sure what in them could've caused a regression though