I've been really liking Kells Uncial https://www.1001fonts.com/kells-uncial-font.html but unfortunately it's pretty much just basic Latin alphabet.

Something similar would be great, although I'd prefer to find one that has distinguished lowercase and capitals - either Uncial but with enlarged capitals or something more script like where the all-caps still looks good enough to write in all-caps sometimes.

Character Set:

Ideally I would like the character set to have the standard Latin, the Latin with diacritics, the standard Greek (or, if it can't be found, I at the very least need either Epsilon or a diacritical variant of E, preferably ę and its capital), and the following letters unique to old English: æ, ƿ, þ, œ, and ŋ, and their capitals.

(æ and œ are not unique to old English, you'll find them in French and many more languages)

https://www.dafont.com/theme.php?cat=403&a=on here are some fonts that contain accents. But maybe not all the accents/chars you're looking for.

What you're looking for is a professional font, something you'll probably won't find for free.

I could be willing to pay.