Really appreciate you documenting all of this you're blazing a path that's going to help a lot of people. I ran into something similar when testing small channel opens with phoenixd. From what I’ve seen, even if the fee estimate says ~1300 sats, the actual minimum can float a bit higher closer to 6,000 sats or more—likely due to internal thresholds or dust limits that aren't clearly surfaced. It’d be great if phoenixd gave a clearer error or min amount prompt when a payment falls short.

Your use of LNbits + Phoenixd as a local, self-hosted stack in low-resource settings is exactly the kind of innovation the Lightning community needs. Once you dial in that minimum for reliable channel opens, your guide is going to be gold for others working in the same constraints. Have you tried checking the logs for clues on how Phoenix handled the failed open?