[Samsung Galaxy Note 8 Questions and Answers] Kamikaze_Ice:
I got WiFi calling to actually trigger the configuration a few days ago after playing around with flashing the CSC different ways checking for behavior.

This was the FIRST time I've ever had that option presented to me on my HTC One (M8) Simcard.

This happened only when using the full CSC Selection pack and only making the change in the "Updater-script" to add "greatlte", as per Flame Red's post.

The last time I did this I used WinRAR to extract and repack the files, instead of using 7zip as usual. Before I had to flash a few times before it would "work". I have no idea why this behavior was observed (hashes and sizes matched, absolutely bonkers).

My process for THAT install was as follows:

***SIM/SD card(s) are NEVER inserted until the very end.

***I didn't check redundancy for steps, so some things may be unnecessary. Just being lazy lol.

I) I do a FULL flash via odin v3.12.7 (edit .ini and set UMS/PATCH=1 and USERDATA=1).

Using official latest native firmware native for my device, so N950N SKC firmware (aka "N950NKSU1AQI2_N950NOKR1AQI2_SKC" on sammobile). I flash all slots BL, AP, CP, CSC (not CSC_HOME) and USERDATA (in UMS slot) AND I use the PIT file I extracted from full CSC.

*Note: Auto reboot is DISABLED. Just to be clear, nothing else changed (so only enabled options are Re-Partition and F. Reset Time. Using a PIT will only auto enable the Re-Partition option).

II) Once flashed, I would manually try to reboot into the stock bootloader by holding all buttons to leave download mode. Once the restart happens the screen goes black and I immediately release ONLY the Vol-down button.

I never stop holding the other buttons (bixby, vol-up and power until I finally get to the stock bootloader. I never could boot straight to the bootloader after a full flash via odin.

III) Again, I keep holding until I'm in the bootloader. This means I keep holding through out the first two blue background android is updating screens.

IV) Once in bootloader, I did ANOTHER wipe via factory bootloader options. I mounted /system, if it even matters, then wiped cache and then did the factory reset wipe option in that order.

V) Once wiped/factory reset, rebooted back into download mode. I do NOT let the system boot or reboot back into the bootloader.

VI) Back in download mode, I flash in TWRP with Odin, using the AP slot and disabled auto reboot in options. I did not flash anything else nor change any other options (F. Reset Time was enabled by default and was left on).

VII) Once TWRP was flashed I manually rebooted to the bootloader (same process as described above).

VIII) Once in bootloader (now TWRP), I allowed /system modifications, and did a Factory Reset (Wipe > "Swipe to Factory Reset"). Rebooted back into recovery via Reboot > Recovery option.

IX) After rebooting straight back into TWRP, I did a Wipe > Format Data, and rebooted right back to the bootloader again.

X) "Installed" "dm-verity and force encryption disabler" as per TWRP thread (Part 2 only), and once again rebooted back into TWRP.

XI) Did another Factory Reset and rebooted to twrp yet again.

XII) Flashed custom rom (Renovate ICE 1.1). Did not reboot when done. Wiped Dalvik+Cache out of habbit.

XIII) Did another Factory Reset and rebooted into Recovery again.

XIV) Flashed full CSC Selection with modified updater-script (used snapdragon AT&T CSC). Did not reboot.

XV) Final "factory reset" wipe and then rebooted to system.

The only differences from my previous methods were all the factory resets in between flashing things and not letting the korean rom to boot at all.

I think the last three were most beneficial.

I can't actually test if it works due to other issues I'm having with AT&T, but this was the first time I've ever seen the wifi calling configuration screens (at last it shows up in options menu.)

Note 8 Wifi speeds now match HTC One (M8) Wifi speeds, suggesting CSC does effect speeds. It's likely this is just one part of the speed issues (read: not the only cause).