I had a look at DLLR. This is what I found.

DLLR is an index of two dollar-pegged stablecoins. One of them appears to be completely centralized like Tether. The other one is overcollateralized by a single asset. In order to maintain a peg, the protocol takes the USD price of bitcoin through a bunch of people who have qualified to be oracles. Anyone who owns enough of the protocol's governance token can be an oracle. Like single-collateral DAI, the protocol rewards people for putting up bitcoins with a variable interest rate and it can shut down issuance when there isn't enough collateral.

I can't find that many designs for a stablecoin. They tend to follow the same few design patterns:

a) completely centralized

b) overcollateralized by multiple assets, including other stablecoins that can be centralized

c) overcollateralized by a single asset, the degree to which is determined by an oracle price feed

a is just fancy banking. do you trust companies like tether or circle? b is dumb because it usually collapses or turns into a proxy for a, like how multi-collateral DAI was eventually mostly backed by USDC.

c is a whole different can of worms. you could have something like a group of people who attest to the USD price of the collateral on centralized exchanges. or you could pull the data straight from a DEX where the collateral is trading against USDT. it doesn't work unless you can either hold oracles accountable or you depend on more centralized stablecoins functioning correctly.

the design of c can be about as trust-minimized as you can get or it can just get silly. but look at the behavior of Sovryn. they deliberately indexed DLLR against a completely centralized stablecoin plus an oracle style stablecoin. it's hard to figure out what they were really thinking here.