The edition I own of Le Morte d'Arthur is the Penguin Classics version in two volumes:
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I'd highly recommend it for someone who's accustomed to reading English literature with old-fashioned turns of phrase (from Shakespeare to the various 19th-century authors or even Tolkien) but not necessarily with archaic, obsolete, or inconsistent spellings of words.
This edition has modernised spelling (familiar words are spelled in familiar ways for today's readers) but retains many archaic words (lots and lots of words never used nowadays, like "hight" for instance), which are all marked with endnotes and listed carefully in an appendix with their translations into modern English. It also has lots of very old-fashioned turns of phrase (phrases in an unexpected order, long run-on sentences, etc), but remains readable for any well-read English literature enthusiast. As well as the endnotes on unfamiliar words, there are also endnotes on some other aspects, such as differences between the Caxton and Winchester versions of the manuscript, or commentary on some apparent contradictions.
Personally, I found reading this a very fascinating experience. To see how sentences were constructed back then and how a story was told, and to learn lots of new archaic words. It may enhance your appreciation of the English language, even if you're already a voracious reader of works from the last few centuries. It may take you a while to get accustomed to the style of writing (battles are described as "So-and-so unhorsed So-and-so, then So-and-so unhorsed So-and-so, then ..." - lots of repetitive prose, lists, etc.) but when you do get used to it, you may really enjoy it.