[Essential Phone ROMs, Kernels, Recoveries, & Other] ultrasuper:
3230 injected and working but super confused about this process.

Stock 036 rooted Magisk 17.1 current slot _a

How I got here:

New phone (7.1.1) -> immediately took OTA (on the phone) to 9.0 (091) -> followed OP to root w Magisk 16.7 -> updated Magisk to 17.1 (via direct thru app) -> Grabbed 036 boot image from OP and patched it w/Magisk and copied to laptop -> Sideloaded OTA, NOT the fastboot one (from Essential's www, following THOSE instructions) -> rebooted directly to bootloader and "fastboot flash" patched boot image ->

Reboot to rooted Sept 036. Done

.

Getting TWRP 3230 on the phone worked but need some things explained. (process below, then Qs)

$ fastboot --set-active=_b
Setting current slot to '_b'...
OKAY [ 0.029s]
finished. total time: 0.0

$ fastboot flash boot twrp-3.2.3-0-mata.img && fastboot reboot
target reported max download size of 536870912 bytes
sending 'boot_b' (48712 KB)...
OKAY [ 2.122s]
writing 'boot_b'...
OKAY [ 0.265s]
finished. total time: 2.387s
rebooting...

finished. total time: 0.201s

# ..Now in TWRP3230. Touch works fine..
# Reboot Menu -> Switch slot back to A
# Create nandroid

$ adb push twrp-installer-mata-3.2.3-0.zip /sdcard
[100%] /sdcard/twrp-installer-mata-3.2.3-0.zip

Continuing in TWRP3230, I install twrp-installer-mata-3.2.3-0.zip, then reboot to bootloader (TWRP comes up, touch works)

Flashed stock 036.img selecting "Boot" (rather than "System" or "Vendor") partition (Right after I mistakenly thought I had forgotten to switch back to the active September slot, so I went into "Reboot" and switched to b and re-flashed stock036.ing there)

Next I flashed TWRP3230.zip followed by Magisk17.1.zip

While looking at the console/log as 17.1.zip was installing, this was indicated:

# - Current boot slot: _a

DESPITE me changing (in "Reboot Menu") to b.

I went back in to "Reboot" and changed the slot to A (figuring it shouldn't hurt) and installed Magisk71.1.zip again.

The same line appears in the console

# - Current boot slot: _a

I repeated one more time to switch the slot (back to _b) and installed Magisk17.1.zip just to see if that console line would change. It did NOT (still _a).

I rebooted to the OS, saw the home screen momentarily, then a toast message appeared (Powering Down), and it rebooted itself to TWRP.. (w NO touch), active slot B.

Plugged in OTG mouse, Reboot (showed active slot B), Powered Down. Powered Up and it goes into TWRP only (no touch).

Now I realized my ORIGINAL September slot was _a. I switched to Slot A, and power cycled, and system came up fine (magisk, rooted, TWRP injected, touch OK.)

Rebooting to recovery (now TWRP) is fine WITH touch. But if I switch (in TWRP) to B, and reboot (goes straight to TWRP only), there is no touch.

Questions:

1) Why is there no touch in TWRP on slot _b? Is it because slot _b had Pie from August? Isn't twrp3230.zip built from August vendor files? OR perhaps because after I explicitly installed the stock036.img to _b I didn't explicitly install twrp3230.zip after and just installed Magisk17.1.zip? (but doesn't installing twrp3230.zip IN TWRP install/inject it to both slots, regardless of which slot is active/selected?) So confused here.

2) Why does slot _b only boot to twrp? and not into the OS? I put the kernel (036 boot image) there, and certainly Magisk17.1.zip. ?