One structural comparison on a Decimal caught, thank you very much 
cmo
restlessronin
ydg33
In case anyone else runs into it—the only other issue I have run into so far is that mix escript.install hex livebook errored due to a different rebar3 plugin (katana_code) also needing to be updated for Elixir 1.17/OTP 27:
===> Compiling aws_credentials
===> Compiling _build/default/plugins/katana_code/src/ktn_dodger.erl failed
_build/default/plugins/katana_code/src/ktn_dodger.erl:582:39: syntax error before: 'else'
_build/default/plugins/katana_code/src/ktn_dodger.erl:747:34: syntax error before: 'else'
...
** (Mix) Could not compile dependency :aws_credentials, "/Users/jyc/.asdf/installs/elixir/1.17.0-otp-27/.mix/elixir/1-17/rebar3 bare compile --paths /private/var/folders/wb/k6crhj493sd7nscrmnzskfb80000gn/T/mix-local-installer-fetcher-ooit_Q/deps/livebook/_build/prod/lib/*/ebin" command failed. Errors may have been logged above. You can recompile this dependency with "mix deps.compile aws_credentials --force", update it with "mix deps.update aws_credentials" or clean it with "mix deps.clean aws_credentials"
But it looks like a fix has already been committed to livebook’s main branch (Update aws_credentials · livebook-dev/livebook@a3baf2a · GitHub), so I just checked out main and ran mix escript.install there, and everything works! No other incompatibilities with 1.17 I’ve spotted yet!
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