Are DJI Matrice 5T accessories compatible with the Matrice 4 Series?

No. DJI Matrice 5T accessories are not compatible with the DJI Matrice 4 Series.

The Matrice 5T has its own accessory range, including the DJI Matrice 5 Series Battery, 515W Charging Hub, DJI AS2 Speaker and DJI AL2 Spotlight. It has three E-Port V3 ports for official and third-party accessories.