It seems FME can not read CityJSONSeq (CityJSON Text Sequences)
https://www.cityjson.org/cityjsonseq/
If you use the reader NDJSON (Newline Delimited JSON) you get the data - however you do not get them converted to CityJSON objects - missing geometry.
Any way to do this either with some Transformers in FME or with a dedicated reader?
Format described in more details in this article: https://arxiv.org/html/2407.00017v1