Acme runs on written decisions. Every project has a one-page brief with the goal, the owner and the date it is due. If something is not written down, assume it will be forgotten. Meetings exist to resolve a disagreement, not to share status updates: status belongs in the weekly note, which every team posts on Friday before 3pm.
Day 1: laptop, SSO and your manager's 1:1. Day 2: shadow a live customer call and write three observations. Day 3: ship one small improvement, however small, to the team's product. Day 4: read the last three quarterly plans. Day 5: present what you learned in ten minutes to your team. Nobody expects you to be productive in week one, but everybody expects you to have opinions by Friday.
Slack for conversation, Linear for work, Notion for documents, Metabase for numbers. The rule across all four: the artefact is the message. A thread that ends in a decision must end with the decision written in the doc, not buried in chat. Access is provisioned by your manager through the day-one checklist; if something is missing after 24 hours, escalate in #it-help rather than working around it.