Installing a .deb is what I was thinking about.
Even a signed tarball is better than curl|sh.
If you have a pre-shared trusted signature to check against (like with your distro’s repos), yes. But… that’s obviously not the case since we are talking installing software from the developer’s website.
Whatever cryptografic signature you can get from the same potentially compromised website you get the software from would be worth as much as the usual md5/sha checksums (ie. it would only check against transmission errors).
That would be “a pre-shared trusted signature to check against”, and is seldom available (in the real world where people live - yes, there are imaginary/ideal worlds where PGP is widespread and widely used) :)