Does Magento support the Greek alphabet (αβγδ) in admin + storefront?

Yes, Magento 2 has supported Modern Greek (el_GR) for years. We’ve shipped Greek-script stores for ten years and there are a few gotchas worth flagging up front:

• Locale pack, install the el_GR language pack via Magento Marketplace or community Crowdin export. Most admin + storefront strings are translated; we backfill the missing ~5% with custom translation CSVs.
• UTF-8mb4 collation, MySQL must be on utf8mb4_unicode_ci (not utf8_general_ci) so polytonic + extended Greek + emoji all store without garbling. We migrate legacy DBs that landed on the older 3-byte UTF-8.
• URL keys, Greek shoppers expect Greek URL keys (/προιόντα/) or transliterated Latin (/proionta/). We default to transliterated for SEO consistency and 301-redirect any Greek-script URLs.
• Polytonic-aware search, Elasticsearch / OpenSearch needs the Greek analyzer (greek built-in) so «σαλαμίνα» and «σαλαμινα» (no accent) match.
• Fonts, some default Hyvä / Luma fonts ship partial Greek subsets. We swap to fully-loaded webfonts (Inter, Roboto, Lato all have full Greek).

End result: a fully Greek-language store that’s indistinguishable from a Greek-built one.