That only goes as far back as to version 1.8 from 2015. Electrum's GitHub releases date back to 0.56 from 2012 (https://github.com/spesmilo/electrum/tags?after=0.57a). I am not sure if it's possible to find versions of the software that are older than that. I think anything older than 3.3.4 can't connect to servers anyway.
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It seems to me that the seed phrase perhaps isn't a BIP39 but a prior version of electrum's seed phrase.

I think Electrum started using versioning in seed phrases since version 2.0 ^[1]. So, if this is correct, then OP perhaps owns a seed phrase that was produced without the current versioning system, so OP must try and find the old code to make it work. Am I right?

[1] https://electrum.readthedocs.io/en/latest/seedphrase.html