Always verify the MD5 checksum of downloaded files to ensure they haven't been tampered with.
If your phone gets stuck on the boot logo, boot back into TWRP, perform another factory data wipe, and re-flash the ZIP package. download android 9 zip file
Some popular sources for downloading Android 9 ZIP files include: Always verify the MD5 checksum of downloaded files
Check the official OnePlus Community support pages for legacy OxygenOS roll-back ZIP files. 2. Trusted Custom ROM Communities boot back into TWRP
Always compare the checksum of your downloaded ZIP file with the one provided on the download site to ensure the file is not corrupted.