I had some trouble understanding the non-standard UTXOS or uses of Bitcoin Blockchain in general, when I first read this email and didn't find any more resources about it
https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-May/012715.html.
Then I understood it much better when I heard this lecture
https://youtu.be/CCeq5PChvukWhere he explained how they create small UTXOS they never spend ( almost like burn) to write some msg in place of the public key signature; this msg could even be a Merkle root for a complete Merkle Tree (for their purposes not for Bitcoin TXs or UTXOs)
& that Catena is different because, among other things, it uses OP_Return for their msgs and just transfer one UTXO back to itself (signed by their own public key) so no UTXO burden is added
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However, I started to search what happened in the last few years since the lecture (2018)
-I didn't find much traces of Catena except in GitHub
https://github.com/search?o=desc&q=Catena&s=updated&type=Repositories(the recent ones have 0 stars, & not MIT licenced except the tree visualizer)
The original one
https://github.com/alinush/catena-javaobviously moved to other projects
Other than that their twitter & other pages last update is in 2019
maybe this one
https://mobile.twitter.com/catenacapitalBut I don't think it is this one
https://mobile.twitter.com/welcomecatena.
-I did find things about the others, but honestly I couldn't figure out from it whether they still use the same methods in the lecture or updated to a better handling of the UTXOS set?
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For example, here
https://book.keybase.io/docs/cryptoThe follow up about Bitcoin use is not there (404 not found error)
But in here
https://book.keybase.io/docs/server/our-merkle-bitcoin-keyDoes this mean (them publishing their key) that they switched to OP_Return method?
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As for Blockstack, I couldn't tell from this,
https://www.investopedia.com/terms/b/blockstack.asp is the new regulations means they have their own Blockchain now or still on top of Bitcoin?
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I mean it could be the problem is solved and they all adopted the use of OP_Return, but is this the case?
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Ps.
I re-checked the non-standard UTXOS curve, there is a slight increase in the last 6 months; ie these uses r not obscelete yet
https://txstats.com/dashboard/db/non-standard-outputs-statistics?orgId=1(420,435 UTXO on 21/8/2021, 420,018 UTXO on 2/7/2021
= 417 UTXO in 50 days)
Unless the curve counts something else more with them
