This report is for educational purposes only. I do not encourage or support any unauthorized firmware modifications. If you're not familiar with the flashing process, please seek help from a qualified technician or Oppo support.
Yes. Flashing custom or even stock firmware via SP Flash Tool is considered tampering. Your warranty is void in most regions. However, for an OPPO F5 released in 2017, warranty is likely expired anyway. firmware oppo f5 cph1723 scatter file