@aral Linux you say?

expand --version:
expand (GNU coreutils) 9.5
Copyright (C) 2024 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by David MacKenzie.

I first thought of GNU sed, as that's as easy as `sed -i 's/\t/ /' my.file`, but then I wondered why you want to do that and realized than it's a feature GNU provides dedicated software for nevertheless.
sed -i also writes in place without you having to use sponge or manually mv the file.