The affected broken release is called lineage-17.1-20210426-nightly-FP3-signed.zip. The one from the week before is lineage-17.1-20210419-nightly-FP3-signed.zip. I already confirmed that the latter one boots. However, I am not sure that is the whole story. LineageOS had some trouble with the infrastructure, with broken builds coming out due to server/signing misconfiguration or rate limiting at some points.
Even more strange - my own local build works as well… Go figure.