I've done a lot of thinking about this over the years.

Ultimately the answer is you cannot, at least with certainty. If you don't own the host, you cannot trust anything that runs on the machine.

A few people have said similar, and that for me is the right answer here. I'll expand on how I used to run my servers, but eventually decided it wasn't worth the effort.

Having said that, there are some things you can do to protect yourself, although it depends on how much you care about your data Vs how much effort you want to put in.

For example, you can disguise your data on disk, by creating an encrypted file on Linux that you mount as a filesystem. Everything you care about runs from there. The ideal solution is you have an encryption key that you store somewhere trusted, that you use to decrypt the volume.

But then of course you have to insert that key each time your machine reboots, such as a kernel update.

You also have to manage and protect that key yourself, otherwise 💥 your data is gone.

Another thing to consider is, is your key in memory or on disk at any time. You need to decrypt the disk without the key ending up on the machine. I passed it over SSH and I assume the LUKS folks know what they're doing about disguising the key in memory, but I don't know for certain. I never looked.

My expectation was that I was doing something outside the norms of how these tools were designed to function, so expect unexpected results.

This isn't to say you cannot trust any provider, it really depends how much you want to trust them.