Harmless in the sense that they aren't dangerous, but they are capable of biting. Source: one was in my headphones a few years back and was biting my ear. I initially thought my headphones were just really itchy.
In my headphones!
shudders
I still check my headphones every time before putting them on now
Hosting video content must be insanely expensive so I have some amount of sympathy for YouTube. However, ads earn such a paltry amount that I can hardly fathom how anyone can put up with it.
The total amount of ad revenue between all sites is only like $12 per user per year. So IMO it is a net benefit to block all ads (save your sanity!) and simply pay the creators of content you like.
Even just one $5 Patreon sub is worth more than all ads I'm likely to see so I block everything I can and IMO my conscience is clear
Firefox beta on Android can use extensions that are designed for desktop. Some only work in desktop mode but so far all the ones I've tried work. The setup is a little complex if the author hasn't marked it as compatible with mobile, but it is possible
I certainly love it! It's one of the first things I install