⭐ Merited by d5000 (2)
A technique which still wasn't mentioned is Bitcoin-based stablecoins without Bitcoin backing. Think of Dai but pegged to Bitcoin. This was already tried out by BitShares in 2015 or so, called BitBTC, but failed to get traction and is now dead, I don't know if there have been other attempts.
There were a couple of attempts on Counterparty but they weren't very successful:
XBTC
BITCOINEX
The reasoning for them was it's not super easy to conduct BTC trades for Counterparty tokens on the platform DEX -- it requires that both parties be online at the time of the transaction to approve signatures. While the DEX itself works great for tokens, it doesn't escrow BTC very well, or is perhaps overly-secure about it.
I know that in the case of XBTC, everyone was given a chance to cash out their token for BTC... BITCOINEX's present distribution looks a little bit more of a mess.
Anyway, just a random anecdote in the history of Bitcoin.