aaand, where to find QT wallet file? all links seem to be dead for years

Well, he said all here:
March 2020 Bootstrap File for Blitz Blockchain:
https://mega.nz/#!ZgMTAaJQ!8OptgNOBN69LnZmiDBwSJ6hOeYcQFgM12Jaxb4g3ARk
Add extracted folder "blitz" to %APPDATA% and run blitz-qt.exe from another drive/directory of your choice.
(Keep qrcodelib.dll file in same directory selected for blitz-qt.exe)
REMINDER: Do not begin staking process until wallet is fully synced with blockchain (green checkmark).
Explorer:
https://chainz.cryptoid.info/blitz/