I believe this issue affects packages with versions before 2018 as well as versions after 2018.
Versions before 2018 cannot be installed, while versions after 2018 can be. For instance,
email@example.com is unavailable, while
firstname.lastname@example.org is available. The difference between them is their publish year. Note that 2.0.2 was just published, which kicked off this series of problems.
Update: This theory appears to be wrong. See @BlackHole1 's comment below :)
Instead, this appears to be because floatdrop's packages have disappeared.
... read the whole story at github.com.