I totally forgot but a SPARTAN, Nicole, is playable in Dead or Alive 4 and is even referenced in later Halo canon so Halo is apparently canon to Dead or Alive because she traveled through time to the 21st Century, if you wanna take this seriously.
"Leave now. There's nothing here for you but a shortcut to hell..." —SPARTAN-458 in Dead or Alive 4 SPARTAN-458 (read as "SPARTAN Four-Five-Eight"), also known by her real name Nicole, is an unlockable character from Dead or Alive 4, created to be like a character from the Halo series. During...
deadoralive.fandom.com
Honestly though, I do not agree with accepting cross-references like this as canon because they are just cameos or references and have no bearings on the main story. So no, I do not take Halo being canon to Dead or Alive seriously. If you believe that, you must also believe that Naotora Ii from Samurai Warriors being in Dead or Alive 5: Last Round through time-travel is also canon but this is contradictory if you believe that Nioh is canon to Ninja Gaiden just because of its references and even then, Nioh portrays some of the same characters that are in Samurai Warriors drastically different in terms of appearance. They are technically alternate universes at this point. Another point, Mai Shiranui's story in Dead or Alive 6 also never states how she is in the world of Dead or Alive as if she always existed yet NiCO summoned Kula Diamond from an alternate dimension but Kula is from the same game series (King of Fighters) as Mai so why is Kula from a different world and not Mai? Also, what about the 4 Virtua Fighter characters? Inconsistencies like these are why I wouldn't take cross-references seriously in terms of overall scope and canon of unrelated series.