Some would say "build it first let's see".
My reply: how am I sure you will believe when it's built. You may consider it magic or voodoo because it is too advanced for you.
When Satoshi publish Bitcoin whitepaper, he faced some skepticism[1] . But Satoshi decide to work/publish the source code and run a full node anyway. Besides, not everyone believe existence of magic/voodoo.
Anyway, anyone can recommend to us how we can easily download our data from Bitcointalk. That is the major reason I want a decentralized forum - to be able to control my data or have copies of my posts/comments saved in my devices so that I can search through them whenever I want, even if the forum nolonger exist. I want something that could serve me well whenever I start moving more often as a nomad, without the internet.
I would recommend the "save page" feature found in many browsers. There's also a convenient print button in many threads.
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You could achieve that with archival and indexing tool. ArchiveTeam website[2] has some list/guide about archiving website. You already found tool for indexing, but you could check different tool such as Recoll[3].
[1]
https://satoshi.nakamotoinstitute.org/emails/cryptography/threads/1/#014815[2]
https://wiki.archiveteam.org/index.php/Main_Page[3]
https://www.lesbonscomptes.com/recoll/pages/index-recoll.html