The very nice support tech told me I should look for a Pace 5268 without AT&T or CenturyLink branding, but those appear to be next to impossible to find. However, if you search for "bonded VDSL2 modem," a few more options turn up. I obviously don't want to waste my time with something that won't work, so I'm wondering what buzzwords and standards compliance I should look for. For example, this is available on NewEgg, and could be promising if it's actually compatible (doesn't look like it supports Annex M, though):
https://www.zyxel.com/me/en/promotions/ ... e_en.shtml
I also discovered that Arris acquired Pace back in early 2016, and further tripped over an Open Source release for Arris/Pace 5268 modems hosted on SourceForge, which could be interesting:
It's entirely probable I'll stick with the rented Pace for a while, but I'd like to better understand possible options.