Only incorrect if you're speaking icelandic. In middle English, þ was used for both voiced and unvoiced.

I've always understood a thorn in the to be used correctly as it's why we see 'ye' instead of 'the' used when referencing old English.

https://grammarpartyblog.com/2011/07/26/ye-olde-mispronunciation-the-long-forgotten-letter-thorn/

Nice! I knew the "ð" character was also a "th" sound, but I didn't realize the subtle differences in pronunciation. I thought it was just used in other languages that don't have the "þ" character.

The big eth always takes me out because it's the same simbol as Đ in south slavic languages that is pronounced like the j in James/Jack.

Thorn would be correct in this case. Eth wasn’t preferred over thorn. In modern english you could in theory split them via voiced and unvoiced but historically they were interchangeable.

The letter thorn that you use is why we have “Ye olde tavern”. Y was used as a substitute for thorn since olde english typesetters didn’t have thorn in the sets they got from Belgium.

And we all know what that makes OP.

What’s the actual difference between voiced an unvoiced? The “th” sounds that same in all of these words