Depends on your phone, but for some qualcomm devices there was a vulnerability some time ago, iirc the OnePlus 15 has a dedicated thread on XDA. I also found this on XDA while trying to find the other exploit:

https://xdaforums.com/t/the-holy-grail-universal-no-bl-root-...

Side note, it's quite ironic, google being so heavily anti-root is forcing people to opt for root access via more hidden ways, making it easier to avoid root being detected.