As OnePlus doesn't always provide download links for all of their OxygenOS ROMs & OTA update zips, we've created an index to put the links in one post so that they're easy to find.
Note: This is not a support thread for issues you may have with OxygenOS ROMs. If you need help installing or updating, feel free to ask here. If you have any other issues, please ask in another thread.
For the sake of simplicity, only signed flashable (full) zips are listed. These are recovery-flashable zips of the full ROM that won't overwrite your data partition unless mentioned otherwise. They can be flashed via local update in Settings --> System --> System Updates or TWRP recovery.
Packages with build tag IN11DA are intended for the following variant:
Packages with build tag IN11AA are intended for the following variant:
Packages with build tag IN11BA are intended for the following variant:
IN2020 units are Chinese units running HydrogenOS out of the box that may be able to run OxygenOS after conversion via local update. They will however need to format /data and wipe cache to avoid bootloop.
Should someone wish to crossflash their device to a regional ROM different than the one present out the box, it is advised they take backup of their /persist partition beforehand by using dd if=/dev/block/bootdevice/by-name/persist of=/sdcard/persist.img (you must have root access, which is not something I'm going to explain here) and moving it to their computer/cloud