TWRP 2.8.7 is a highly recommended, known reliable version. Or it might not be a bad idea to update to current/latest version, which is 3.3.1-0
http://dl.twrp.me/m8/
Although not that much has changed in TWRP for this device. Anything 2.8.7 or newer should be okay.
I'd definitely stay away from older (2.7.x.x) TWRP versions, as they will not be compatible with current (or anything but really old) custom ROMs, as well as not compatible with your firmware (hboot, radio, etc.)..
Related note, thanks for posting the getvar output. This let me to verify that you are on the last firmware (Marshmallow) that is available for the M8 (again, this refers to hboot, radio, etc. and not the same as the ROM). Which is the best place to be for both stock and custom ROMs.
---------- Post added at 09:45 AM ---------- Previous post was at 09:42 AM ----------
I know you got the drivers somewhere else, but in case others read this thread and want to download HTC Sync:
The link I gave above, for me when I click it, it says "Download unavailable" for a second, then automatically redirects to a working download page. But here is the direct link to working (at least for me) download webpage:
https://www.htc.com/us/support/software/htc-sync-manager/
---------- Post added at 09:50 AM ---------- Previous post was at 09:45 AM ----------
I'd recommend to stay away from stock recovery. It won't fix your issue, and is rather useless at this point. The only real use for stock recovery, was when this device was still getting OTA updates (for installing those updates) but that hasn't happened for years. So stock recovery serves absolutely not benefit, as far as I know.Custom recovery is far more useful.
Fastboot flash TWRP (2.8.7 or newer). To fix the storage issue, try: reboot to TWRP. Select the TWRP "Wipe" option, then tap the "Format data" button. This is not the same as a wipe, this formats the data partition. Which in a lot of cases, fixes the data partition corruption errors (which it seems like you have).
---------- Post added at 10:01 AM ---------- Previous post was at 09:50 AM ----------
I don't actually use the M8 as my daily phone for quite some time. I just pop into these forums from time to time to help folks, as there still seem to be people coming here for help from time to time, and not a lot of "helpers" anymore. I do still keep the device as a backup. I actually had to fire it up last year, when I broke the screen on my OnePlus 3T and was getting it fixed.
As far as custom ROMs, iof you want anything newer than Marshmallow, I think you are pretty limited to Lineage, or maybe a few other AOSP ROMs. If you want the IR blaster, you may be limited to Sense ROMs (can't remember). I tended toward the modified stock Sense ROMs myself, as I wasn't a big AOSP ROM user on the M8. I hopped around a bit between S.Team ROMs, and maybe Skydragon (Sense version), Viper, and a couple others. Hard for me to remember too specifically at this point.
---------- Post added at 10:02 AM ---------- Previous post was at 10:01 AM ----------
There is a button for that, if you feel compelled to use it