I have a sapper (pre-sveltekit) project from 2019 that doesn't build. I needed to make a tiny update and neither my current computer nor my previously configure

I have a sapper (pre-sveltekit) project from 2019 that doesn't build. I needed to make a tiny update and neither my current computer nor my previously configured netlify autodeploy can produce a build that works. I have no idea, my first guess was that one of the sapper people didn't pin the version of an important dependency, but the project was simple enough that I just wrote a new one from scratch.