So the Storage Lead Developer of Scaleway reached to me saying that they had real issues with buckets with more than 1m+ objects, the databases can't handle it. He said my bucket was really stuck so he couldn't do anything.
They know I'm migrating so he's keeping a eye on it and we keep in touch while it's ongoing.
They will offer this month's bill, which is cool.
Sometimes stuff goes wrong, 
75% as of now. The majority of what's left is broken objects so it will take longer
Stuck at 85%. About 250k objects are missing but their metadata is supposedly broken. I'll see tomorrow with the provider
The thing is, the background jobs queue is huge now, because there is a backlog of 3.5 millions jobs. So Redis is using 5-6GB of RAM which is messing up with the server.
Since this is getting pretty bad, I decided to switch to the OVH bucket with the missing files. I would have preferred not to but it's the best option right now.
Background jobs are processing right now, faster and with less errors because the bucket is usable. From what I see the number of jobs is still going up. Let's wait and see.
I disabled full text search so that I could turn off Elasticsearch, because I'm very short on RAM.
sidekiq is only processing 50 jobs at once, increasing it seems to exceed the pool of postgres connections
@admin Congratulations on the progress!
@admin I often refer to myself as an "IT guy", but I have no idea what you are doing right now 
Wow, it's 2x to 6x more efficient. The backlog size is finally going down!