[G2 Original Android Development] Eiion:
I don't have TWRP right now. I'm on Stock 5.0.2. Also, apparently TWRP isn't available anymore on XDA for the G2. I spent quite a bit time last night figuring out how to get TWRP and learnt that apparently I first had to install an older version of it before being able to update it to a newer version. I learnt about Autorec for KitKat and Lollipop but (since I'm on Lollipop) couldn't find the one for the latter version or much information about it.

As for the rest of your instructions - I'm not sure I even understand what all of that means correctly, not to mention how to do any of it without detailed instructions to avoid messing things up and bricking my phone.

Sure, but as said: "without any experience of installing custom firmware" - I'm technically not without any knowledge, but when it comes Phones and Firmware I'm a complete noob - though, I'm trying to learn after avoiding it for the past 7 years (which is when I got my 1st smartphone, the G2 after having used the Nokia N95 for 7 years).

But ok, what I'd like to understand though is where I went wrong following the instructions literally word for word to end up with the abd commands not working (i.e. adb not finding the files) in order to downgrade the bootloader. What information was missing from the instructions that would have made the commands work?

More question arose after reading back a bit in this topic: Do I understand it right that NFC is mostly buggy, that the IR blaster doesn't work at all with LineageOS and that there's another bug with 'swipe up to HOME' with the newest releases of LineageOS? Again, I'm not experienced at all with custom ROMs but was under the impression that LineageOS releases (in general) would be fully working as in all features of supported phones would work? (Also, for noobs like me, a section "Features not working" in the original post would be helpful to get a better (easier) understanding. I know, it states what does work so I guess one could figure everything not mentioned doesn't.)

Now, I decided I could go with LineageOS since the G2 isn't my main phone anymore for the past few years i.e. I'm not dependent on it to work 100% at any time, making it easier for me to risk trying out Lineage and thus a newer OS compared to Android 7.1.1 on my daily driver. But still, not being able to use the IR would be kinda... sad.

Anyways, I assume there's a way to go back to the original Lollipop or even Kitkat firmware if I'd ever want to? So I guess I'll keep trying getting LineageOS to work and learning something along the way, to become more confident when it comes to installing custom ROMs.

Thanks for the info to skip forward to step 3.

---------- Post added at 12:32 AM ---------- Previous post was at 12:00 AM ----------

The crucial part to copy files with adb was to be in the adb path in the command prompt. After changing directories to that folder I was able to start the sideloading procedure. So I guess this is what I did wrong last night.

When sideloading lineage, at "(~47%) I got a "adb: failed to read command: No error". I went ahead with sideloading gapps - which finished without issues. Unsure about the first sideloading process though I decided to start over with "Factory Reset, then Format data / factory reset" and sideloading lineage - just to get the same issue at ~47%.

At this point the last to lines showed on the phone were:

Patching system image unconditionally...
script succeeded: result was [1.000000]

So instead of 'lineage-17.1-20201015-nightly-d802-signed.zip' I'm now going to try 'lineage-17.1-20201008-nightly-d802-signed.zip'.

EDIT:

That one gave me a "Total xfer: 1.00x" in adb - no idea if it went up to 100% this time as I was looking up the previous issue in a browser tab, but at least this time I got no "adb: failed to read command: No error" - so I guess/hope that this time everything went fine? Anyways, I'm now continuing with sideloading open_gapps-arm-10.0-nano-20201020.zip again.

EDIT 2:

Thinking of it, is it an issue to combine the newer recovery image with the older lineage zip? (I guess I'll find out in a minute after rebooting the phone...)

EDIT 3:

I'm currently in the process of setting up the phone after restarting it. So I'm assuming that everything went well disregard the old/new version mix.

EDIT 4:

After playing around with the phone for the past 3 hours everything seems to be working fine (for now at least). That's great! Also, knowing what I know now installing the ROM (when it finally worked) was pretty easy - I should have dared to give it a try sooner.

But as a little TL/DR of this post of mine above, let me repeat the questions (and add three more) hoping to get some more information:

1, Do I understand it right that NFC is mostly buggy and that the LG G2's IR blaster doesn't work at all with LineageOS?

2, My mistake from last night (and earlier tonight) that was preventing me from putting the files in '/sdcard' via adb was that I didn't the run the commands from within the right folder?

3, Is it known what the issue was at ~47% where I got a "adb: failed to read command: No error"?

4, Is it known why I couldn't successfully sideload the newest 'lineage-17.1-20201015-nightly-d802-signed.zip' while the older 'lineage-17.1-20201008-nightly-d802-signed.zip' apparently worked fine?

5, I cannot find where in the setting I set the phone to turn of WLAN when in standby (i.e. screen off). That's what I've always set from Android 4.2.2 that was originally installed on the G2 up to Android 7.1.1 on my Axon 7. Is this setting not available anymore in LineageOS 17.1 or if it is, where can I find it?