The IRS has been (and remains) seriously backlogged due to all the new tax laws and extra stimulus filings, as well as unprocessed 2019 returns still left over from the COVID shutdown. Lots of other folks are still waiting (some since mid-February), so please continue to be patient. Also see:
Tax refund delays could continue as backlog of tax returns is growing, tax advocate says - CBS News
It is also sending out Stimulus #3 payments in batches, and will take a few more weeks to complete them all. This one comes to you separately (and automatically), not as part of your 2020 tax refund. You can check the status here:
Get My Payment | Internal Revenue Service (irs.gov)