A tangential issue: As you approach the low ends of dust limit (or below the dust limit), obviously the economic value becomes negligible.

This has the effect of lowering the risk to the point that its no longer really worth anyones effort to self-custody that.

"SQL" (which is how zaps work), becomes a fine solution at or below the dust limit, because the risk is so low.

The other viable alternative at that level is CashU.

I think its entirely possible that this is how the landscape eventually develops:

500,000+ SAT = BTC Mainchain 1000 to 500,000 SAT = LN .1 - 1000 SAT = SQL / Cashu / etc