In SQL Server 2016, transaction log writing was enhanced to support multiple transaction log writers. If the instance had more than one non-DAC node in [sys].[dm_os_nodes], there would be one transaction log writer per node, to a maximum of 4.
In SQL Server 2019, it seems the maximum number of transaction log writers has been increased. The system below with 4 vNUMA nodes (and autosoftNUMA disabled) has eight transaction log writer sessions, each on their own hidden online scheduler, all on parent_node_id = 3/memory_node_id = 3 on processor group 1.
Click through for the proof.