Go to customerconnect.vmware.com and log in with your VMware account. If you don't have one, click "Register" – it takes 2 minutes and is free.
If you have a 2021 timestamp requirement, use ESXi 7.0 . For ESXi 8.0, use the Broadcom portal and ignore the 2021 label—no 8.0 ISO exists from that year. Download -2021- Vmware Esxi 8.0 Iso