Windows 10 does support Sinhala and Tamil through Language Packs, but many users still face issues because:
For 99% of home and office users, the native Windows 10 kit + Helakuru (optional) is the best free combination. Free Download Sinhala Tamil Kit For Windows 10
specifically designed for Windows. It allows seamless switching between Sinhala and Tamil and produces Unicode-compliant text, ensuring your typing is compatible across modern websites and documents. Helakuru for Windows Windows 10 does support Sinhala and Tamil through
Although Windows includes "Iskola Potha" (Sinhala) and "Latha" (Tamil), some old documents require extra fonts. Download these free, legal fonts: Free Download Sinhala Tamil Kit For Windows 10