What are some best practices to improve team cohesion?

As simple as it sounds, people usually bond over common interests and goals.

Given you all work in tech and probably have some overlapping projects, that could be a good place to start. For example, if there's a new piece of tech that is new to many people on the team, form a study group or better volunteer to build training on it that can be as simple as a lunch and learn (pull in people who want to collaborate and help as it comes). Curating and sharing good resources is another relatively low-effort way to get engagements (favourite books, articles, podcasts, etc.).

Both as an IC and a Manager, I found that having occasional office hours and AMAs tend to bring people together and provide an avenue to gather input / obtain feedback.

The best way to build deep relationships is to just lend help to others when the opportunity arises. There is a good Taro video on building relationships here.

You can bond a lot over personal interests that are non-career related as well, but that's situational and may take some time to discover.

Here's a couple things we've tried from my past across Meta and Robinhood after the pandemic hit:

• Virtual offsites - At the end of the day, it's hard to beat spending $$$. The one I remember the most was chocolate making at Robinhood. We all got shipped a chocolate kit, and on the day of the "offsite", we got into our kitchens and pointed our Zoom at it. A chocolate chef walked us all through the instructions, and it was fun seeing what everyone's kitchens looked like and how well (or poorly) people followed the instructions and made their chocolate. Virtual escape rooms are a thing as well, but I haven't tried it.
• Board game night - There's a lot of good websites that allow you to play board games online, and we did this several times back at Meta. This was our favorite: https://skribbl.io/
• Online coworking - The idea is that everyone gets into a call with no agenda and just works with their camera on. When people need help or just want to take a break, they can start a conversation. The idea is to mimic physical coworking as much as possible. Since you're a senior engineer (and you also seem like a lead), you can encourage the conversation a bit by asking people what they're working on and trying to help them proactively.

Fostering remote/distributed teams is very difficult, but it can be done with enough hard work and genuine care for your teammates. I also recommend this playlist to help: [Taro Top 10] Growing Fast With Remote Work In Tech

Best of luck!