Recently switched teams and finding myself struggling in the new role

Sorry to hear about your current situation - These team switches can be hard to navigate. Here's my thoughts:

• Request people's time aggressively - Learning a new stack is hard, and I wouldn't expect a mid-level engineer to have superb learning speed yet. Because of this, I recommend doing as much pair programming as possible, ideally with your tech lead or tenured senior engineers on the team. If they're too busy, maybe you can find a tenured mid-level or junior engineer on the team: They could be more incentivized to help you as they can claim credit for your onboarding.
• Spend time with other people - If you're going into the office (I heard Apple is doing RTO more now), go into the office as much as you can, especially if you know relevant people will be there. Have team lunch, go to offsites, hang out with folks around the water cooler/microkitchen - Building trust is all about getting more face-time in. Try to set up 1:1s with tenured engineers on the team, so they can help with build that codebase fluency - You can suggest bi-weekly so it's not overwhelming. If you're full remote, I've linked a relevant resource down below.
• Leverage your manager - Low coding velocity isn't great for a mid-level engineer, especially one looking for the senior promo. Maybe your manager can help pair you with the people described above - It's in their best interest to increase your productivity. A sample question can be: "I'm having trouble grokking this new tech stack - Is there someone on the team who would be a good fit to pair program with me for the next ~1 month to get me up to speed?"

Related resources:

• Strategies For Recovering From An Unproductive Streak
• Building Relationships Better And Faster In A Remote Era
• Picking Up New Tech Stacks Quickly As A Mid-level Engineer

I think pair programming can be really effective here. Could you define some well-scoped task and ask for a 45 min meeting (I'd literally send the cal invite as "pair programming") with someone who is familiar with the tech stack? Rather than view it as someone holding your hand, try to make it a 2 way exchange of information - maybe you could share your workflow, or just share context on the task you're working through.

Another tactic is to start with a good junior/mid-level eng on the team, in case you're worried about feedback/judgment from someone more senior.