Hi @Canapin
We also had to write some Ruby begin rescue end wrappers when we imported our vB3 attachments into Discourse; but in the end, we got almost all attachments and avatars and profile images migrated.
When we started, I had no experience with Ruby and Rails; but now I am a big fan of Ruby and Rails, thanks to Discourse; and write a bit of Rails code every day now.
It’s good to learn a bit when migrating, I think, if you have the interest.