السلام عليكم ورحمة الله وبركاته In my country, this is what is taught to recite in tashahhud. I know there are multiple versions that can be recited at the beginning, but is the one that we are taught permissible and authentic: ....ٱلتَّحِيَّاتُ ٱلْمُبَارَكَاتُ ٱلصَّلَوَاتُ ٱلطَّيِّبَاتُ لِلَّهِ

Ustadh AbdulAziz al-Haqqan

All the ones authentically reported are correct to say and we went through this in manhaj assalikeen so study it may Allah reward you.