[Magisk] 73sydney:
Just a quick concise reply.....

Oh theres more than bats up there in my belfry.....

Maybe theres some issue when you join those two sentences together, but Ive never come across that recommendation before, probably as i never "upgrade" from one stock ROM to the next and keep data, im actually boring in that i always clean flash. So it might be true, ive literally never used the upgrade path and the HOME_CSC method. As for just singling out the first sentence, flashing a file alone in AP in the sense of installing magisk...in the guide most use for my device at least, its the method in the guide

My personal method every month is to:

- Download latest stock ROM via frija

- Extract into ODIN folder

- Backup my apps and data (Migrate - free and used for years now) and copy off device (because clean flash = /data bye byes)

- Put S20+ in Download Mode (power off, hold down Vol + and Vol -, plug cable in)

- Run ODIN on PC

- Load AP,BL,CP, CSC files into respective matching slots

- Load the AIO.tar (which contains the multi-disabler patcher - which decrypts data, installs TWRP and stops stock recovery from being reinstalled, along with bluetooth library patcher and bootlogo patcher (to remove annoying Samsung unlocked bootloader nonsense)) in USERDATA

- Hit Start in ODIN

After a little automated trip into TWRP where it flashes the multidisabler, bluetooth and bootlogo patcher zips and reboots, i end up at the setup wizard where i do the basic setup, enable USB debugging, do a quick adb reboot recovery, where i flash magisk and let it do its work, then reboot to system again and install the magisk app, and rename it. Then i copy my default folders back, including /Migrate, where i install the Migrate flash and helper modules from and restore all my apps and data (196 apps or so), including an app (Classic Power Menu - free and great dev) to give me (amongst many things) easy access to rebooting to recovery....

Then i flash my magisk modules, lsposed, reboot...

Then i reimport my magisk Deny list from backup, my lsposed backup, my HMA backup, and add latest randomly named magisk app to the HMA root blacklist template and reboot, and largely my life is back to normal

Well, apart from the fact that since Samsung has spannered Watch 4/5, anytime i flash the phone, means i have to reset the Watch to reconnect it (all previous tricks, including one i invented for Watch Active 2 (my previous wearable) to avoid a reset now fail), so ill have backed the watch up too (3rd party apps at least via adb and my own scripts), reset it, debloated it via adb and via my own script bulkinstalled (restored) the 3rd party apps, along with modded Samsung Health Monitor (thanks to @Dante63 - nicest person you'll meet on XDA), then pushed my ringtones, alarm and notification tones to it and then reconnect it to the phone. Then the joy of setting the watch faces and apps and settings again, because of course none of that is included in the Samsung online backup (rumours abound that with Pixel Watch entering the fray we're getting a proper granular backup of such things). The last part takes a good half hour of faffing about on its own to get things back to "normal"

I do this every month....Ive on occaision when time was short (often testing 3/4 custom ROMS a week) on previous devices (pre Watch owning days), dirty flashed a custom ROM of same over previous, but generally ill clean flash, because eventually the dirty flashing paradigm will go horribly wrong, and its usually when you have also been too lazy to do a backup and you think"oh it will be fine, ive dirty flashed 10 times before..."

...sometimes it "isnt fine" and resetting up 190+ apps from scratch isnt fun times at 1AM :(

Note: For the insomniacs amongst you: for some background on the AIO.tar mentioned above, see here (and the OP of that thread for basic concept):

https://xdaforums.com/t/s-20-series...tooth-and-fix-safetynet.4240755/post-87516321

Nope, i never thought vbmeta was technically needed, but i always add it if i comment as its whats been noted in docs over the years.....like i said, it could use some simplification

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And now for something completely different...

All this sudden cheerleading by you for Momo is most unbecoming :)

Almost as bad as Vera De Milo