Hiring runs on signals. A recognisable employer is one. A degree from a well-known university is another. An engineer who has neither, and who is applying to a company in a country where their institutions mean nothing, needs a third — and the most reliable one available is work anyone can go and read.
Why it works better than a portfolio
A personal project shows what you built alone, with no constraints and no review. A merged contribution to a maintained project shows something harder to fake: that you read an unfamiliar codebase, followed its conventions, wrote something a maintainer was willing to accept, and responded to criticism without falling apart. That is much closer to the actual job.
How to start without wasting six months
Pick a tool you already use and are mildly annoyed by. Fix the documentation first — it is genuinely useful, maintainers are grateful for it, and it teaches you the codebase's shape at low risk. Then take a small, well-defined issue. Avoid large refactors of projects you have just met; they are rarely merged and the effort is unrecoverable.
The part that is not about jobs
Software built elsewhere encodes assumptions from elsewhere: address formats that do not fit, name fields that reject legitimate names, date handling that assumes one calendar, payment flows that assume a card. Those assumptions get fixed when someone affected by them shows up and fixes them. That is a reason to contribute that has nothing to do with a CV, and it is the one with the longest half-life.