- Edited
AGI I wouldn't, but I can give you the md5sum so you can check if it's the same and then it means the bits are identical, regardless of where you downloaded from (even the most shady site):
45e55a87cfeb061319858f46ed6b6aab
No problem to install that if the phone came with Android 8.0?
Probably not, I think problems arise with new releases only due to TWRP compatibility.
Edit: OK it could be that Paranoid Android didn't work because the previously installed OxygenOS changed the device firmware somehow. But each OxygenOS comes with firmware, so they probably wouldn't have such problems ever. @degen said he had to downgrade his firmware before he could install Paranoid Android after trying the latest OxygenOS. I can imagine once you installed an older OxygenOS like this 4.0.3 version we are talking about, you would have an earlier firmware afterwards that is still compatible with Paranoid Android. Just speculation, but it could work I guess.