Weblate

Weblate is a web-based translation management platform that connects to your repositories and keeps localization work in one place. It commits translations straight to Git, reuses a translation memory, applies glossaries and plural rules, flags issues with quality checks, and can suggest machine-translated strings for review.

Open source projects use it to coordinate contributors across dozens of languages, and product teams use it for apps, manuals and support content, and it can be integrated into your stack.

Hosting it yourself keeps your source strings and translation memory private, has no per-seat pricing, and the database plus Git history make backup and restore straightforward.