official Developement is postponed with no date to take it back up.
Ergo: Yes its abandoned.
Last schine update is april 2021, since then its been small community pushes.
But community activity is stalling too for the past 6 months.
Development has stalled due to lack of funds. See Schema's comment here:
...However, there is still a small community (especially on Discord) and at least three notable major modding projects are currently ongoing in some shape or form. And there is always the hope that Schema can come back someday.