A **super hacky** workaround is downloading an old butler v15.17 binary from here: https://broth.itch.ovh/butler and replacing the butler binary in your itch installation. What makes it **super hacky** is you need to overwrite the v15.18 binary to trick itch into thinking you have the latest butler version, otherwise itch will update from 15.17 to 15.18 again and overwrite the binary that works. Well, if this is fixed in 15.19, itch will think you're on 15.18 and overwrite the hacky workaround, so it won't mess up your itch installation for eternity, I think. Only do this if you know what you're doing.
My butler binary was at
~/.config/itch/broth/butler/versions/15.18.0/butler