Installing LineageOS zips in TWRP results in “Error 7”

There are watermarks saying “cm to lineage migration” on every screen

My device is officially supported, but there’s no zips for it on the download page. Where are they?

My device is not officially supported, but I’d really like to give LineageOS a try. Can you support my device?

A build for my device disappeared? Where’d it go?

I found a bug. What do I do?

Can I have xxx feature added?

My device doesn’t pass SafetyNet!

Can you enable signature spoofing?

Where does the updater app store the downloaded zip?