Depending on which country you and your employing entity are in, this could end up netting you all of the disadvantages of self-employment with none of the benefits.

E.g. in the UK, HMRC will determine your tax status based on, amongst other things, how much control your 'not employer' has over the work you do. So if GitLab were to treat you as just another member of the team, you'd run a big risk of ending up treated as an employee for tax purposes, but without any of the rights accorded to employees.

TLDR - talk to a tax professional who understands the regulations in both your and your "not employer's" jurisdictions.