We formally maintain a number of Open edX repos. See Open edX Backstage: repos owned by arch-bom.
We have a weekly on-call rotation: https://2u-internal.atlassian.net/wiki/spaces/AT/pages/16387065/On-Call+Arch-BOM (private link). Maintainership duties initially fall to the on-call engineer:
All PRs are triaged within a week of opening.
Authors get feedback on a weekly basis on changes they make.
Any security updates are applied within in a week of them being published.
Work that should be taken on by the team will be ticketed on the team’s project board: https://github.com/orgs/edx/projects/11/views/1, then reviewed a few times per week for progress.