How do I update to Marshmallow on a rooted Bell HTC One M8?

I realize this is probably asked fairly often, but I did try to find the answer myself. So I thank you and apologize in advance.

In any case, I've been using lollipop for some time on my M8 now. It is rooted and S-On. As a result, I can't simply OTA up into Marshmallow. I bought this phone used, and I believe it was Bell, but I'm uncertain. I was hoping to update to Marshmallow (and keeping my files intact if that is at all possible), but am totally at a loss as to what I should be doing. For one, not a whole lot of threads about Bell, so I'm unsure what files I should be using, but beyond that if someone could give me a nudge in the right direction, I'd really appreciate it.

To get things started, my fastboot getvar all is:

Code:

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C:\WINDOWS\system32>fastboot getvar all
(bootloader) version: 0.5
(bootloader) version-bootloader: 3.19.0.0000
(bootloader) version-baseband: 1.25.21331147A1.06G
(bootloader) version-cpld: None
(bootloader) version-microp: None
(bootloader) version-main: 4.20.666.1
(bootloader) version-misc: PVT SHIP S-ON
(bootloader) serialno: SH445WM-----
(bootloader) imei: --------------------
(bootloader) imei2: Not Support
(bootloader) meid: 00000000000000
(bootloader) product: m8_ul
(bootloader) platform: hTCBmsm8974
(bootloader) modelid: 0P6B16000
(bootloader) cidnum: BM___001
(bootloader) battery-status: good
(bootloader) battery-voltage: 0mV
(bootloader) partition-layout: Generic
(bootloader) security: on
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: dcdaa6e0
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0
all: Done!
finished. total time: 0.060s

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