I don't have advice lol but I also struggle with singing even though I would love to improve

start slow by hitting random notes on your piano and matching them with voice. nothing in this area is innate to us and takes months to get better at, just keep at it, don’t give up!

at some point once it becomes easy, you want to start increasing the volume (like with all of the exercises) to make forward progress, there are backing tracks on youtube playing random chromatic notes, you can also adjust the speed of the video. try to hit a lot of them at a speed that's on the edge of comfortable for you. the next step after that is to sing melodies, arpeggios, etc... interval barks is also a good game to do daily.

the thing about this exercise is that it's not just about mastering using your voice, it's about internalizing the pitch of the note in your brain

Thank you for your answer Dima. That really helps.
I'm just so confused. If it's true that it is not innate to us, how come random people out there singing random songs.
The approach you're discribing is a nerdy way of doing it, and I love going the nerdy way. But most people probably don't do it that way and just sing songs. So I don't get what's going on.

My answer appears to have disappeared.
When you do interval barks, what feedback do you get? If it says sing P8 above the note you hear, and you try to do that, what does it say you tried?
That is a starting point. If it says you did P5 the problem is different to when it says you did m9.

Hi Grietje,
thank you for your question.
It is somewhat random. I somehow made it to level 5 on interval barks. But it's really difficult for me. I click the sound repeat button a lot and fiddle around with my voice trying to find the right pitch. But to answer you question: Most of the time it's a halfstep or wholestep above or below, so m9 or m7. But random stuff like m13 does also happen.

Okay, so that gives something to work with. Full disclosure, I am a singer, so take it as you find it. I think your problem my lie in the first instance in getting the right starting pitch. When I started on interval barks, I couldn't get it to work as I took my starting pitch an octave too high. If you download vocal pitch monitor on your phone (or device of choice) you can check your pitch 'take over', I find a lot of people who start singing have difficulty with that but repeating ad nauseam gets them to sing the right phrase. Checking where you pitch with that monitor is a good idea.
Also, I would suggest not to set interval barks to voice, but to the regular piano instead. And do the vocal register test, as that can make a difference. Even do it again if you have done it at the start.

@Ed Di people who can do that naturally got their training somehow implicitly at a young age, for example while singing songs with their parents on the car trips. it’s a bit of a chicken and an egg problem, because not having this skill will discourage you from singing further, which is needed to develop it in the first place, so most people think they don’t have “natural talent” and give up. but once you have it, you start using it and only getting better at it.

also it’s not that uncommon to not be able to match the pitch well even among musicians. but inability to do so imo hinders (or at least slows down) the development of relative pitch

if you like nerdy stuff, here is one more tip: listen to your voice matching the pitch. you’ll hear it fluctuating and searching for it. notice how long it takes before your voice settles and try to minimize that delta as much as possible. eventually you’d be able to match the pitch instantly. there is a lot going on in our brains in that process and controlling the vocal chords is only the last tiny step in the whole pipeline

also make sure you actually sing the right pitch, it’s not uncommon to sing a consonant interval like a fifth/fourth or even a third instead when starting out, you’d be surprised

Thank you all for your encouragment and tips. That really helps on a mental level. I'm feeling a lot better now about my singing journey. Thank you very much, wonderful people