[Magisk] HippoMan:
Thank you for all this!

As it turns out, I managed to solve this in a totally unexpected way, and I still don't fully understand how it ended up working.

I originally had a partially installed but uninstallable version of Magisk Alpha 26401 on the device. By uninstallable, I mean that after I patched the boot image and tried to flash the result, it always said that it had to do more in order complete the Magisk installation and then to reboot. But whenever I selected "OK" at that point, it never completed anything and never rebooted.

This is what originally prompted me to think I needed to delete /data/adb, but doing so didn't change anything ... which is consistent with what you said in the previous message.

So, I gave up and decided to do a factory reset. That, at least, seemed to work.

There's a Nothing-2-related thread where a developer posted ROMs that can flash the Nothing 2 OS with a built-in Magisk Standard 26401 module. I did that, but with the latest OS version, which was one version higher than the version that had been installed on my device up until now, and this ROM install indeed brought up the OS successfully, and I then performed the initial OS configuration.

Then, I went to the Magisk manager, and here's the first unexpected surprise: there was a Magisk Standard manager that had been installed, but also, the Magisk Alpha manager from before the factory reset was also still there. I would have thought that the factory reset would have gotten rid of that leftover Magisk Alpha manager, but that obviously didn't occur.

Looking at both Managers, the new Magisk Standard manager showed that Magisk was not installed at all, but the leftover Magisk Alpha manager was now showing that Magisk was indeed fully installed ... and it turned out to be totally functional now.

I'm guessing that the ROM-with-built-in-Magisk-Standard flash somehow fixed whatever was preventing the Alpha Magisk installation from completing before.

So, I just uninstalled the new Magisk Standard 26401 manager and decided to stick with Alpha.

And another surprise: instead of installing the newer OS version, the flash of that ROM-plus-Magisk image didn't install the new OS, but instead, my old OS version was still live. I decided to accept that version for the time being.

Then ... luckily, there's an OrangeFox version that works on the Nothing 2, and since nandroid backup/restore are quite desirable to me, I went to install OrangeFox.

The installation is supposed to go as follows (and this is how I originally successfully installed OrangeFox a few weeks ago on the same Nothing 2) ...

(1) Download an installation ZIP file for OrangeFox

(2) Unpack it on the desktop computer and then also "adb push" that same ZIP file to the device's /sdcard.

(3) One of the unpacked files is "recovery.zip", so do a "fastboot flash recovery.zip". This is supposed to initialize OrangeFox and also boot into it.

(4) Then, from OrangeFox, flash the other ZIP file from /sdcard. This is supposed to complete the installation and then boot back into the OS.

HOWEVER (!!!) ... that didn't work.

When I tried to flash "recovery.zip" per the instructions, fastboot said the flash was successful, but I remained in the bootloader. And even worse, at this point I could no longer boot back to System, nor to Recovery. And I couldn't even get fastboot to accept a Shutdown command. Every attempt of each of these that I tried just kept me in the bootloader.

So, I figured that since my device seemed to be nicely hosed, just for the hell of it, I decided to see what would happen if I "fastboot flash" the entire OrangeFox ZIP file from step #1 above, rather than just its contained "recovery.zip" as specified in the installation instructions. And surprisingly, this got me into a working version of OrangeFox, and I was no longer stuck in the bootloader.

Again, this differs from the official installation instructions and differs from how I successfully installed OrangeFox a few weeks ago.

And also when I was in OrangeFox, I noticed that my latest nandroid backup that I took right before trying all this actually was still availabie. This at least is not surprising, because it resides in a directory called /sdcard/Fox.

So then, again just for the hell of it, I decided to perform step #4 as I listed above ... re-flashing the same ZIP file, this time directly from /sdcard. At this point, I figured that I have nothing to lose by trying this. And happily, my system rebooted successfully!

Yesterday, right before starting to go through all of this, I took a full backup of my apps using SwiftBackup. So, I installed the SwiftBackup app, and sure enough, after starting it up, it properly requested root and Magisk granted it. I then restored everything except the older Magisk Alpha manager that was part of that backup.

And now, everything got restored!

So now I'm just in the simple but time-consuming phase of running some of those apps so that they will request root, and doing some additional system configuration. I'll do all of this in my not-very-ample spare time over the next few days.

Interestingly, this is exactly what I originally wanted to accomplish: remove Magisk Delta from the device and install Magisk Alpha, without changing the OS version nor anything else.

So even though I had these problems with uninstalling Magisk and with getting OrangeFox to install via its official instructions, I have now achieved my goal.

This occurred in a crazy, unexpected manner, but all's well that ends well!