So I read this and this and solved my problem. Basically I bind /temp/download to /media/$USER/download and then I can set the download directory in Chromium and Firefox snaps to /media/$USER/download and my downloads go where I want them. This was actually harder to figure out than it should have been.
To download a web page along with its scripts and styles etc:
wget --page-requisites --convert-links --execute robots=off https://www.example.com/whatever/
Here’s the home page for Guide to Assembly Language Programming In Linux… includes a zip file with assembler source code for examples.
To download a file from the web and send its contents to standard out, try this:
wget -O - -o /dev/null https://www.unconfusable.com