[Samsung Galaxy Note 8 Questions and Answers] Kalm_Traveler:
Glad you made the right device choice :)

As far as HTC vs Samsung firmware I don't really have any experience with HTC. As you see in my sig, I've only owned 1 LG and 4 Samsung devices so far. As far as explaining what I have done on this Note 8 N950N, initially I rooted it out of the box (well, a couple days later), then flashed that S8 multi-CSC selector file choosing T-mobile. I then flashed my own modded version with some T-Mobile Note 8 N950U CSC files, but that didn't make any difference so I tried flashing [MENTION=4107827]TEKHD[/MENTION] 's S8+ Tmo WiFi-calling pack on top of all that. It 'worked' again with everything except WiFi Calling, which is one of the two main sticking points for me.

After that, I decided to make my own zip with TEKHD's installer script and others.xml as a base, but built using T-Mobile Note 8 files, so I grabbed them from the SM-N950U T-Mobile firmware from Sammobile, deodexed the few of them which had odex files, then zipped it all up and flashed that after doing a full Odin N950N SK Telecom factory re-flash and reset.

Same results as before... most/all of the extra features offered by TEKHD's others.xml file, definitely working VoLTE, HD voice dialer with working video calling and call recording option, but no trace of WiFi Calling in any settings menu or status bar icon. Launching the TmoWfcPref.apk action with a shortcut app showed that the toggle slider and preference options are greyed out.

To answer your question about de-bloated, that just means I've been deleting all the Korean pre-installed bloatware, most of the Samsung apps, etc manually. I have not tried an N950F-based ROM yet but that is one of my next options since technically the S8/S8+ folks who have used these zips to gain Tmo Wfc were on F variants, so it's possible that their firmware includes some files necessary for the Tmo software to function, and those files are absent or different incompatible versions on our N950N.

We should be fine with the firmware besides the bootloader as you mentioned, though if I were you I would just install TWRP and flash a 950F-based ROM rather than trying to get Odin to accept factory firmware.

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Basically I have 2 theory steps left before I give up and try an F-based ROM. Today I was poking through the handful of files that are flashed to add Tmo Wfc to the S8/S8+ international F variants, and found that TmoWfc.apk (the T-Mobile Wifi Calling menu app) contained references to 3 framework libraries that are present in the T-Mobile ROM but not on our SK-T ROM so I copied them and their .oat accompanying files over, set the file permissions correctly and rebooted, no change. Factory reset, still no change. I did not find anything in any of the remaining Tmo-patch files that seemed to be referencing any other files. I also compared the bools.xml file inside framework-res.apk between both and flashed over the T-Mobile settings basically (the values are mostly the same between the two but T-Mo had a few things enabled that SK-T didn't) which totally tanked the system but nothing another factory reset didn't fix (while keeping the updated settings in tact).

My next step was/is going to be to compare all the files referenced in those APK's between the Tmo and SKT ROMS to see if the overlapping ones are different in size, and if so try swapping the Tmo versions over but I am super new to this so right now I'm just on a steep learning curve trying to figure out how this all works. This has been my first legit mod project and I've already had to learn how to deodex APKs, decompile and re-compile APKs, unpack compressed .img and .img.ext4 files, manipulate files and folders in Linux, and edit installer scripts. At this point I'm 100% positive that the N950N can do T-Mo's WiFi Calling, really anything that can do VoLTE can because they run on the same underlying IMS technology, one is just over a WiFi connection and the other is over an LTE connection - the trick is figuring out what setting(s) and/or executables or libraries are still missing and/or wrong versions.

I might switch back to the Note 5 for a bit so that I'm not as inconvenienced by having to factory reset my phone every day trying to get this sorted.