[Nokia 2.2] SB3P:
OK, here's the procedure how to make it work (from scratch, i.e. default ROM with locked image):

1. Unlock bootloader (if you have unlocked it already, skip this step).

2. Update to Android 11. You can do a full security update if you wish to (please note I haven't tested from which security update you're safe to patch, but it's very likely all of them would work with this procedure, at least from my knowledge).

3. Check your active partition slot with this command:

fastboot getvar active-slot

Save it somewhere or remember – it will be needed in the next step.

4. Do a readback with SP Flash tool of boot and vbmeta partitions. You need to know your partition slot for that task (A or B), so you won't flash a wrong image later, possibly breaking your OS. I did a readback with MTK6761_Android_scatter.txt file and I took from it the proper partition lenghts. So, if you for instance search for a boot partition of slot A (boot_a), you should copy the start and lenght values from the properties as shown on the screenshot below:

View attachment 5386451

It is recommended to seperate these two images for a readback – so, in total, you should have two entries, first for a boot partition and second for vbmeta:

View attachment 5386475

When adding an SP Flash Tool entry, I recommended to call it with following scheme (where {partition}_{slot} should be repaced with parition name):

{partition}_{slot}.img

...because you're doing a readback of a single partition, not a full readback as you did before to unlock the bootloader. Moreover, you don't even need to extract the boot image, hence it is an image of a single partition already, not a ROM image containing multiple images inside of it – so you can flash it directly after patching.

5. Boot your device, copy the boot image you got from the readback and patch it with official Magisk Manager application on your phone (of course, install it first, if you don't have it already). Currently I tested the 23.0 version, so take that in mind the newer/older versions may not work at all and produce an incompatible image format. I won't guide you how to patch images with Magisk, you should know that if you're read this guide.

6. Flash the image and patch the vbmeta image to disable the verification. The command to do that is as follows:

fastboot --disable-verification --disable-verity flash vbmeta <path-to-vbmeta-image>
fastboot flash boot <path-to-magisk-boot-image>

(replace <path-to-vbmeta-image> and <path-to-magisk-boot-image> with correct image paths)

7. Reboot your device and if there's no bootloop at the process, you're done. If not, flash stock Android 11 image you got from the readback and reboot. If you will boot successfully, then it may be due to some security update being incompatible with magisk (which is very unlikely to happen, but I wouldn't say that's impossible) or due to not disabled boot verification with vbmeta. If you can't even reboot with the stock Android 11 image, you're likely did a readback wrong, reflash the stock Android 9 image and try doing all of the steps again, making this time sure you took the correct values from the scatter file.

(Similar procedure may work for Android 10, althrough I haven't tested it yet.)

EDIT: Some fixes to the instrucions.