use ssh variant...

.gitmodules

@@ -1,6 +1,6 @@
 [submodule "dep/streaming-data-types"]
 	path = dep/streaming-data-types
-	url = https://gitea.psi.ch/lin-controls/streaming-data-types.git
+	url = git@gitea.psi.ch:lin-controls/streaming-data-types.git
 [submodule "dep/flatbuffers"]
 	path = dep/flatbuffers
-	url = https://gitea.psi.ch/lin-controls/flatbuffers.git
+	url = git@gitea.psi.ch:lin-controls/flatbuffers.git