Google would be very happy if you used its Chat application, so glad it pushed it beyond the bounds of the actual app. Last month, the tool became available to regular users (who do not pay for access to Google Workspace), and now integration with Gmail is also available to them. But it is not turned on by default, so if you want to use it, you have to dig into the settings menu.
First open the side menu in Gmail, scroll all the way to the bottom, and tap “Settings”
Scroll down to the “General” area of the list. The first option should be “Chat (Early Access)”. Touch it. Tap “Try it” in the pop-up alert.
Gmail is restarting, which can be a little tricky. Open it again if it does not appear automatically and you are greeted with a new line at the bottom of the interface. “Mail” is your default mailbox, “Chat” takes you to the official Google Chat application with all your text conversations, and “Rooms” is the ongoing conversation view. (Like Slack, but basically useless.) You can switch between the three views at any time.
If you want to remove Chat and the bottom navigation bar completely, and you might want to, just follow the steps above again.