there are trackers and possibly malware on rcyoutube , i would recommend to avoid it.

no MP3 download available

It looks like it start the process but never download. :(

Converts to MP4, not MP3.

no download button

Statt zu downloaden, wird Werbung in neuen Tabs geöffnet. Grausam.

Downloads often fail, which is frustrating.

It's a spam. Avoid !!

Tidak ada tombol apa2

ほぼ広告ウイルス

détecté comme nocif par Ublock : je désinstalle

When you click on the icon of this addon. It instantly redirects to a belgian domain by the name of conv2, but also downloads through apiyt, a malaysian site.
Once "download" is clicked. The website redirects you to sippansy, an advertising provider service, which then automatically redirects you to a pornography site, most often "Chaturbate" or "RealLifeCams"
The addon has zero warning that it will redirect to both sippansy and by extension these porn sites.
It also has no 18+ warning for children under the age of 18. Endangering minors.
The cookies recorded were:
mywatchtones 1 cookie
apiyt 9 cookies
conv2 4 cookies
realcam 7 cookies
chaturbate 15 cookies

I recommend avoiding this malware.

Takes you a third-party site (I can do that for myself) and then you have to disable your various security addons so it can redirect you and shower you with adverts. Uninstalled