Short answer: it depends on the role, and many don't need a diploma. The open postings show it varies a lot. Some ask for a degree outright (the Lifted (Upwork) role requires a bachelor's or higher). Others, like the TELUS Digital AI and RWS TrainAI Community evaluator roles, list no degree in what I can see. They ask for things like being comfortable evaluating online content, or a country or one-per-household rule. Turing's role prefers an English, Literature, Journalism or Creative Writing background plus annotation experience, but it doesn't say a certificate is mandatory.
Why a form might still ask: many platforms use a standard profile that has an education or certificate field for every role, and it may not be mandatory. If the field is marked optional, leave it blank. If it blocks you from submitting, I can't tell from the data whether it's a hard requirement. That is decided by the platform, so its support team can tell you. Don't pay anyone for a certificate to get a job, and don't send documents to anyone who contacted you first. The scam checker can help if something feels off.
If you have no degree, start with roles that don't list one. If you've applied to a specific platform and hit this, tell us which one. Others who've been through it can say whether they got in without a certificate.