Im so glad I replaced the battery on my 3+yr old Oneplus 6T. I could probably use it another 3yrs. Take it to a local shop if you dont diy : r/ oneplus
OnePlus 6T and 7 Battery: Replacement Part BLP685 - iFixit
Remplacement batterie OnePlus 6T - Centre Réparation Paris Montgallet, Porte Maillot, La Defense