Monday's feature drop for the Pixel phones included a fun nugget that wasn't in the official changelog: it appears you can now use both a physical SIM card and an eSIM on 5G networks at the same time. Previously users who had both installed and operational were limited to LTE speeds, even if their carrier had 5G service in the area.
According to several commenters on the Pixel subreddit, 5G service has appeared for those users after receiving the March OTA and feature drop. That's in addition to notable new goodies like compatibility with underwater cases and improvements to the Recorder app.
If you're using both a physical SIM and an eSIM with your Pixel 5 or 4a 5G, and you don't see 5G service in your reception icon, try disabling dual-SIM functionality in your Settings menu. When you reenable it you may see the 5G icon.
- Pixel subreddit