Yoana or Yohanna? Registry office tomorrow!

It depends on whether you want that H pronounced.
I would read them as :
Yo Hannah with a stress on the H
Yo Anna to rhyme with spanner.
(NW UK)

@MegMarchHare , one way round it is to write something like Moana as Mo-a(r)-na or Mo-aa-na. The IPA is [məʊˈɑːnə].

My rough calculation was considering the population of Scotland and NI, vs England and Wales. So yes, small minority. I know rhotic accents exist in England, but they are also a very small minority in England. Very "back of a fag packet", but I stand by it until corrected with a better calculation!

Could Yolanda/Jolanda work?

I think you're overestimating the average person's awareness of this stuff. It sounds like you are have a rhotic accent and you live in a mostly non-rhotic country (even if you live in NI or Scotland, the "Roarsome" cards you see in the shops are developed for a general UK market, and I'm sure you wouldn't see them if you lived in the US). Therefore, you are very aware of it - and it sounds like you have advanced knowledge of linguistics which gives you the terminology to explain this. Most people on MN are non-rhotic English speakers who just have no reason to ever give this much thought, nor the knowledge to unpick it. You will be waiting a very long time for the typical Baby Names post to start off "So, I'm a non-rhotic speaker living in a non-rhotic region, and therefore I'd describe the sound I'm looking for as Arna", and you'll be waiting just as long for other posters to understand it. I think it's the sad fate of rhotic speakers (you) and pedants (me) to have a slight heart-sinking feeling when we see pronunciations transcribed this, and then to shake it off!

A small minority of people in the UK have rhotic accents
Really?

No, the “least bad” way is to make no assumptions at all and simply to state your frame of reference. Surely you don’t think that rhotic speakers read all texts originating from outside their native region in an internal Joanna Lumley voice, just in case?

Let me give you an example. Every kids’ birthday card section has at least one card in it featuring a lion or a dinosaur and the words “have a Roarsome birthday!”. In my head I read it as “Roarrsome” every single time and have to remind myself that it is a pun if you don’t pronounce your “r” sound.

If Yohanna isn't a "proper" spelling but a compromise for English speakers, I'd go with the Johanna spelling and just tell people how to say it, they will soon learn.

In Greece Ioanna (that's an i at the front) is pronounced 'yoanna' - lovely name!

The letter Y is rarely used in the German language - the letter J in German has a similar sound to the letter Y in English.

I think Yohanna gives you neither a German nor an English spelling.

Yohanna in Spanish is pronounced similarly to a soft English J sound, in Hebrew, it is pronounced similarly to an English Y sound.

DH is German and his sister is called Johanna

they pronounce it Yo hanna - no ah sound

I do think on a UK centric site that it's the "least bad" way to assume non-rhotic pronunciation. A small minority of people in the UK have rhotic accents, and many people who haven't studied this get mixed up about where rhotic speakers even place their Rs... Just listen to any child trying to do an American accent. Very few people are familiar with the international phonetic alphabet, and almost any vowel sound, when transcribed in normal letters (like "ar" or "ah"), is open to multiple interpretations.

@TimeandMotion , you forgot the Welsh.

@CandidPlum , write it as Johanna. Yohanna looks wrong and Yoana looks like Yo-na.

In this case, I advise Yoana. It's spelt pretty much as it's said (even though I've never heard of it before). You'll get a mix of "Anna" and "Arna" pronunciations, and maybe even the odd "Yona", but I think a good chunk of people will read it as intended. The Moana analogy helps.

Yohanna is almost always going to be read as "Yo Hannah". Which just makes me think of someone shouting "Yo, Hannah!".

That's from an English perspective, I can't speak for Germans. I also can't work out what the difference is between your two intended pronunciations - they both read like they rhyme with Moana to me.

I knew a Johanna and it was pronounced Yo-hanna, but sounded more Yuh-hanna really. I prefer Johanna over Yohanna and Yohanna over Yoana which I think will get really horribly mispronounced as Yo-ner as 'oa' generally makes an O sound as in boat.

This

With those spellings I would say
Yo-Hannah
Or Yo-Anna

Why not go for something simple like Yanna?

I prefer Johanna too. I wouldn’t know how to pronounce the other versions mentioned (even after reading this thread!)

Yes - I also have a German family member spelled Johanna. It is pronounced Yo-hanna. I've never seen it spelled with a Y.

I would use Yohanna, but would prefer to spell it Johanna. My dc had a German friend named Johanna but pronounced Yohanna.

Definitely Yohanna! It's beautiful. The other is just not as pretty. I would read Yoana as rhyming with loner.

Although there is absolutely no need to spell it phonetically, reading the (slightly bickery!) comments above re pronunciation, there is definitely scope for non-German people to pronounce Yohanna wrong, if they have only seen it written not heard it spoken. They'll rhyme it with manner rather than farmer. But that is easily corrected and not a problem.

Fair enough. All OP (and you) need to do is to specify at the beginning which variety of English is being used as the reference point rather than assuming that all readers speak the same way.

The best approach is, of course, to use the International Phonetic Alphabet but that is not readily available on most keyboards and not easy to understand without the accompanying key.

Apologies.

A failing on my part then as I cannot think of any other way to write that sound, that makes it clear what I mean.

Not intended to be offensive!

I think Joanna and Johanna are great names. I really don't like the Y spelling at all.

Is it really spelled with a Y in German?

If your daughter is living in the UK she will have to spend her whole life explaining spelling and pronunciation if you go with the Y

Do you want Yo-anna or Yo-arna?

I prefer the arna ending so Yoana