Upload audio only to YouTube, as shown in the recorder with a black image e.g. B?

Does anyone know (I have an older Huawei, but it can still keep up with normal apps.) How I can simply upload it to YouTube, for example when I record something in the standard app "Recorder"? I've already tried .m4a to .mp4 converter, it doesn't work. I just want to be able to upload audio only using my Huawei cell phone (preferably also via app, just stories without showing my face → no, I don't want to spread conspiracy theories or anything else, but rather about my life). Videos become so large after 8 minutes that there's no more memory available. And actually I would just like to have a black background or something very simple as a background. At first I'm mainly concerned with AUDIO.

Have already tried 10 apps. Does anyone know something for me that ONLY works with my Android phone? I don't have a PC or anything else.

Greetings to everyone and have a nice day, thank you to everyone who helps me or read through this question.

You could make an unlisted live stream on Youtube with your mobile phone and mask the camera or something and then later set the livestream to open because it is saved in youtube so you don't need an app and you don't need a memory because you just talk you don't need the most blatant quality

Yes, but that would really be so severely unprofessional. It can't be that difficult to put an M4a or MP4 on a black MP4 underneath. Imagine if there has to be a changing picture underneath. Hehe

It's also not difficult if you had a pc I don't know myself with the smartphone at all I use my cell phone so seldom that I'm used to cell phone keys and thus write twice as fast as on the smartphone ^^ but well, power director would be no cut app for the mobile phone but have a watermark from dennen