Getting this too. First time trying to download this. Running Windows 10. Trying to install it at a non-default location (not sure if that matters but fyi in case it does).
On a second attempt I got this:
Something went wrong
itch-setup, v1.18.0, built on Apr 10 2019 @ 07:28:23, ref 57838bc373361f2c8938336674247f869999e862
broth.itch.ovh: HTTP 404: Invalid file requested
github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs.(*conn).tryConnect
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs/conn.go:148
github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs.(*conn).Connect
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs/conn.go:56
github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs.(*File).borrowConn
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs/file.go:329
github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs.(*File).readAt
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs/file.go:473
github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs.(*File).ReadAt
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/httpkit/htfs/file.go:444
github.com/itchio/itch-setup/vendor/github.com/itchio/arkive/zip.readDirectoryEnd
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/arkive/zip/reader.go:476
github.com/itchio/itch-setup/vendor/github.com/itchio/arkive/zip.(*Reader).init
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/arkive/zip/reader.go:80
github.com/itchio/itch-setup/vendor/github.com/itchio/arkive/zip.NewReader
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/arkive/zip/reader.go:73
github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr.(*ArchiveHealer).heal
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr/archive_healer.go:261
github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr.(*ArchiveHealer).Do.func3
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr/archive_healer.go:102
runtime.goexit
C:/Go/src/runtime/asm_386.s:1321
github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr.(*ArchiveHealer).heal
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr/archive_healer.go:263
github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr.(*ArchiveHealer).Do.func3
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr/archive_healer.go:102
runtime.goexit
C:/Go/src/runtime/asm_386.s:1321
github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr.(*ArchiveHealer).Do
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr/archive_healer.go:209
github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr.(*ValidatorContext).Validate.func5
C:/Multi-Runner/builds/58469115/0/itchio/itch-setup/src/github.com/itchio/itch-setup/vendor/github.com/itchio/wharf/pwr/validator.go:138
runtime.goexit
C:/Go/src/runtime/asm_386.s:1321
while installing
Error during warm-up