Yeah, like others have said, while Electrify = Photon - 4G, Electrify M is a whole other animal altogether. I think it's the US Cellular version of the RAZR M or something like that.
Anyway, if XDA doesn't support the Electrify M (and I wouldn't expect them to... they don't much like US Cellular), check out this forum that does
. Bonus: the administrator/owner uses an Electrify M, or at least he used to. So there are people there who know about it.
Also, while the Electrify M does use a SIM card, it's strictly for LTE. Now, if you're getting your phone (voice) over LTE (VoLTE) that's something a lot of us (and them over on TUSC) might not be familiar with as VoLTE isn't set up in the US yet. On a regular Electrify M in the US, data is typically handled over LTE (SIM) and voice is handled over CDMA, so you can talk on the phone while surfing the web. That's one of the perks of the LTE phones.
Samsung Galaxy S3 / US Cellular / d2usc