Lucia

Lucia is also Finnish and Estonian. The name day for Lucia in Estonia is December 13.

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Source: https://en.m.wikipedia.org/wiki/Lucy (Feminine name variants section)

Also Czech: https://cs.m.wikipedia.org/wiki/Lucie - listed as a variant

Also Romansh:
Source: "Vornamen in der Schweiz. Prénoms en Suisse. I nomi in Svizzera. Prenoms in Svizra" (1993) published by the Association of Swiss registrars
https://sursassiala.ch/2015/01/15/familienforschung/
https://nossaistorgia.ch/entries/A39DB2bJDNY
https://www.portraitarchiv.ch/portrait?page=57

Also Dutch: https://www.meertens.knaw.nl/nvb/naam/is/Lucia

The standard Polish form of this name is Łucja, but Lucia has also had some use. Last year (2021) 3 baby girls were given this name. As of January of this year, there have been 487 Lucias in Poland. I think this name might be potentially even more confusing in Poland than in English-speaking countries pronunciation-wise, even though Polish is a phonetic language, or maybe actually because of it. Aside from the three pronunciations of Lucia that exist in English, I'd imagine a lot of Polish people would assume it's pronounced LOO-chah (where the ch sound is a bit softer than in the English and Italian pronunciation, and the ee sound is very short). Lucia pronounced this way also exists as a normal Polish nickname of names like Łucja or Lucyna, but also ones like Lutosława. A Lucia could celebrate her Polish name day together with Łucja/Lucja (4 March, 25 June, 6 July and 13 December), or perhaps with Lucyna (30 June), Lucjan (7 January, 13 June, 26 October) or Łucjan (26 October). I can see the nickname Lusia (pronounced LOO-shah) being used by Lucias who pronounce their name with the s or sh sound rather than ch.

Also Provençal and Languedocian: https://ieo-oc.org/spip.php?page=article&id_article=300 --- Source: Institut d'Estudis Occitans

Lucia is also Estonian. The name day for Lucia in Estonia is December 13.

Also Banatswabian: https://ofb.genealogy.net/famreport.php?ofb=zichydorf&ID=I1347&nachname=Bentz&modus=&lang=de
https://ofb.genealogy.net/famreport.php?ofb=zichydorf&ID=I20941&nachname=Schein&modus=&lang=de

Also very common in South America.

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Means "Light" in Latin.

Also Slovene: https://sl.wikipedia.org/wiki/Lucia

Also Corsican: https://fr.wikibooks.org/wiki/Pr%C3%A9noms_corses
https://co.wikipedia.org/wiki/Frassetu
You'll find numerous bearers on social media.

Also Estonian: https://et.wikipedia.org/wiki/Lucia_(eesnimi)

Also Occitan: https://fr.wikipedia.org/wiki/Liste_des_pr%C3%A9noms_occitans (Source: Institut d'études occitanes)
https://opinion.jornalet.com/Lucia-roulet-casaucau/blog/1005/ensenhament-occitan-bilingue-shau-e-la-vergonha-damora --

Lucia is also celebrated in Romania on December 13.

Lucia is also the Slovak version. [noted -ed]

This is also a guy's name, and I am not making this up. It sounds really good for a guy, better than for a girl I think.

Where in the world did you hear that it was a guy's name? Lucia isn't a guy's name, it is a girl's name. The Meaning & History section clearly states that it is the feminine form of Lucius.