> in some ancient version of english with characters that I've never seen

There are really only 3, or if you want to stretch it 5, English characters that you might not be familiar with as characters: þ, ƿ, ð, æ, and ȝ. And the last of those isn't even present in Old English; it's a Middle English thing.

If you were reading something in Old English, the use of ƿ wouldn't really be an issue - the issue would be that nothing made any sense. Recognizing the characters used, or not, is irrelevant.

As you note, the recognition issue is an issue of fonts and not of alphabets. Compare wikipedia's sample of blackletter: https://commons.wikimedia.org/wiki/File:Calligraphy.malmesbu...