"To cut the story short, I had to accept that there is nothing I can do with the networking issues and there are likely to be significant “bursts” of dropped packets that will cause disconnection of our MySQL8 cluster nodes.
So we know there is very likely an infrastructure problem. The question is, can we mitigate it on the application layer?"
That seems unwise. It's on DigitalOcean, so they could have migrated to different VPS instances and checked to see if the problem followed.