It will depend on the 359 tail number, currently:
From this wiki it looks like that one will have the old, slow, but functional WIFI because it doesn't say "ViaSat":
Best Seats, Amenities, & Experiences on Delta's A350-900
3501 N501DN…delivered TLS>ATL Aug 5 2017…entered service Oct 31 2017…flew the first A350 flight DTW>ICN Nov 18 2017…C+ installed at MSP Jan 10-Feb 2 2021.
The alternative is nonfunctional ViaSat WIFI due to the satellite issue (but would have been faster had the satellite not had a problem).