Any 18650 with a rated capacity of more than 4Ah is a fake. They will usually be very low capacity. The low weight and the hollow sound when you tap on it is good indicator of that too.

There are a number of reputable sites for buying 18650 cells. Stay away from Amazon and Aliexpress, they are full of fakes.

Ideally they would provide a graph showing how many watt hours it will output from minimum to maximum load. If it supports multiple voltages, there should be a separate line in the graph for each voltage.

The new car is worse. They will sell your info to the highest bidder.

Unless the filament ships in a foil lined bag that’s vacuum sealed with desiccant and an indicator card, you should assume it’s wet.

yt-dlp is a fork of youtube-dl, which was released in 2006.