[OnePlus 3T Questions & Answers] redpoint73:
You aren't being specific enough when you say "same method". The general method is often similar. But you will virtually never use the

exact

same steps when rooting different Android builds (such as Nouget vs. Oreo). In particular, you always need to use updated versions of files for TWRP and Magisk. By definition, the root exploits will change between Android versions. So using old version Magisk is basically asking for a "soft brick". Not a real brick. It usually just means you need to use the correct version Magisk in order to recover. Or at worst, flash recovery image (or restore TWRP backup - which you should

always

have a backup of the stock ROM before rooting) then root with the proper files. Don't know anything about your old phone - but I'll guess this is what happened (which is a common enough scenario).

Similarly, you should also use the most current version TWRP. Older versions may sometimes work, depending on the situation. But Oreo (vs. Nougat) in particular, TWRP had to be updated to be compatible. Meaning you

must

use a Oreo-compatible version of TWRP to avoid problems. Short story, use current version TWRP to avoid problems.

Current versions are:

TWRP 3.2.1-0

Magisk v16.0

Also proceed with the knowledge that this device is very hard to brick. Just flashing TWRP and Magisk will not brick it (not a true brick anyway - a "soft" brick is easy to recover from as already described). Just make sure you are using Magisk for the OP3/3T (not some other device) and the risk is virtually zero. Even in the case of a brick, this device has an unbricking tool. Just be sure to take the following precautions:

- Make a TWRP backup of the stock ROM before you flash Magisk (always amazed at how many folks skip this!) or otherwise have the stock recovery image available in case anything happens. Basically always have a backup plan!

- Find the unbrick tool, and again have it available (at least bookmarked) in case you need it.

- Most importantly, read and understand all the steps and concepts

before you begin

. As another already mentioned, it seems your knowledge about some of the concepts is a bit lacking.

---------- Post added at 10:30 AM ---------- Previous post was at 10:06 AM ----------

Beta or Stable doesn't matter. I don't know if I've ever seen a root guide specific to the Beta version, so I'm not even sure what you are talking about.

As far as the guides being for Nougat, I've already addressed that above. Basically, everything is the same, except the file versions (use updated TWRP, Magisk) so that is why nobody has bothered posting new guides for every OOS build.

DM-verity is just a warning screen that appears when you reboot or power-on the phone. It will go away and continue to boot normally after 5 seconds, or just press the power button to dismiss the warning.

Once the phone has TWRP and rooted, you

will

have the DM-verity warning screen. If you like, you can flash a patched boot image, so you don't see the DM-verity warning screen on reboot/power-on.

You will also have a very similar (but separate) warning screen once the bootloader is unlocked. Unlike the DM-verity screen, the bootloader unlocked warning is impossible to be removed. The only way to remove it is to relock the bootloader, which I would

strongly warn you not to do

on a modified (TWRP and root) device! The bootloader unlock warning screen is just something you live with if you are rooted (just wait the 5 seconds or press the power button to skip it).

There is also the unlikely event that DM-verity will outright prevent the OS from booting. But this shouldn't happen just from flashing TWRP and Magisk (at least not if you've done it properly). Even if this happens, just restore your TWRP backup, or flash recovery image, and start over - checking what you did (cause you probably did something wrong).

This is so vague, as to make it hard to figure out what you are even asking.

In short, No.

Long answer: Some apps will not work with root, such as banking apps and Netflix. But the Magisk "Hide" feature should work to conceal root and make these apps work. It's a whole topic in itself, so read up in existing threads if this applies to you, and you want more info.

Other than that, there isn't anything with Magisk root that I would consider an "issue" and make me want to unroot.