I have not kept up with "all" the ways, nor the best. There are some browser add-ons specific to youtube, and some which handle as many sites as conform to some standards and/or the developer has added support for, and then there are some (almost, since you still need the browser to get the URL) standalone apps, both web based, and client side based.
I forget the name of the browser add-on I was using, but the developer stopped updating it and either a newer browser version or youtube changing something, broke it.
I think I have (or had) Video Download Helper add-on to Firefox, but eventually found it a bit limiting, and it does not support Youtube downloading with Chrome browser because google won't allow it in their web store if it does.
Next I was using 4K Video Downloader app but the free version, which stopped supporting multiple simultaneous downloads. Finally I switched to
JDownloader2 app, which is very full featured and works great, with
very frequent developer updates, but there is a bit of a learning curve to it, if you don't want to accept the defaults, things like which resolution, framerate, and codec version of each video you want to get.
There are lots of other tweaks I made to JD2 over time as well, but it has a built in plugin for youtube that you can make adjustments on. You might try JD2 with the defaults and see if it does what you need (since it's freeware), then only change what you need to.