There is definitely a method. Check this out, and let me know if you have a question about anything. https://xdaforums.com/t/installing-stock-rom-on-oneplus-11.4664076/ Disclaimer: I don’t own a oneplus phone, but I have a lot of experience with custom roms over the years.
I can’t switch to any other os than arch, the AUR is a must have for me.