Update: the #systemd merger is in progress. We recommend NOT updating your devices which are running #postmarketOS edge until this is complete.
We are currently working through some issues with the changes to https://build.postmarketos.org
A full explanation of the changes and our recommendations for migrating your devices to systemd will be published once things are ready!
In the mean time, refresh https://build.postmarketos.org at will
EDIT: this should no longer be necessary, please ensure your pmbootstrap is up to date (latest git master) and if you did run the below command reset it with pmbootstrap config -r mirrors.systemd (after updating)
if you're trying to use pmbootstrap and run into an issue because the systemd staging repo can't be found, doing the following will prevent it from attempting to fetch the (now missing) repo
$ pmbootstrap config mirrors.systemd none