[One (M9) Original Android Development] Pfony:
Hi there, yes thanks for your comments. After reading the "echo in voice calls" is gone I give it a try and to end the pain of my interlocutors;).

FIRST of all: BEST ROM ever:D:cool:, and I am on board since LOS 14.0=7.1.2 for my htc-one-m9 and went through all successors (LOS 15.x, 16.x, 17.x and 18.0)

So to quote and answer my own questions:

referring to 1. the "echo problem":

it is definitely SOLVED !!!! (ohh, I am so happy .... for my interlocutors :ROFLMAO:)

referring to 2. the "dirty flash":

hmm, maybe it would have worked if I disabled the PIN before, but I couldn't foresee that so I cannot confirm or deny that it would have worked

referring to 3. "color temperature/live display" feature:

yes it is back and working, and I love that (my eyes are gonna thank me in a few years)

Now I'd like to share my steps and the experiences I encountered.

At first I tried a "dirty flash" just by simply installing the latest 18.1-rom via TWRP over my existing 18.0... ==> It booted, but I had a PIN lock before and now it didn't accept my PIN anymore (wonder what would be if I had disabled the PIN lock? would it still ask for a PIN?) So I reinstalled (dirty flash) once more but still it required the PIN that wasn't accepted anymore ==> so I (had to) wipe: cache/dalvik+system+data (yes I am very sure I did also the "data") and was convinced to "install from scratch" by choosing these partitions....phone booted into the "first time boot question sequence (language, time zone, etc questions). But today I installed "osmand~" (from fdroid) and surprisingly all my downloaded maps from before the new installation of 18.1 where shown :unsure:.

So I took a look into internal-storage/android/obb/ and yes there where the maps.

Questions:

a) is this possible to still have this data on my phone even if I wiped "data" partition in TWRP (3.4.0)?

b) my phone is set to 2 languages: "1.english (us)" and let's say "2. german (german)" but when I write a message (and the keyboard is set to german by the "world"-icon on the on-screen keyboard of course) the german text is underlined in red for all the words (this was not the case on LOS 18.0). To get this working I have to switch manually the "spell checker" option to "german" to get rid of the red underlining, but when switching in between to english then all english words are underline....very annoying. Could someone confirm this behavior (for maybe your 2 languages)?

c) I still discover having problems with bluetooth connections to my car. When having my phone connected to the car and doing a phone call the audio output is by my car's speakers, so far so good....but after some time (maybe a minute or so) suddenly the audio is switched back to the phone's speakers. So I hastily pressed the power button again to get the phone's audio output by the car again (I am not sure whether this would work if I just do nothing and wait :unsure:). This was also on 18.0 and was reported by me. Any ideas?

One more thing I wanted to be thankful: the built-in camera app is now the same as in LOS 17.x (again) which I absolutely preferred more than the one from LOS 18.0 (which was strange, had less options, and took a long time to get started by pressing double-power-button)

So for me it is the best of all the ROMs I ever had for my m9. THANK YOU SO MUCH all Maintainers!(y):cool::)🤩🥳

ps: can anybody recommend a nice (not google-play store) weather app. I am missing so much my weather under the clock as on LOS 16.x and before. Any suggestions for getting both clock and weather together?😇