you could run your own dnssec servers (not too hard). and monitor the DS records for your domain at the TLD. have there been any reported cases of law enforcement changing DNSSEC (e.g. adding a DS record)?

i agree there's probably no way to keep a machine hosted at a company secure from law enforcement. also why i suggested storage and anything in ram on the machine can be considered compromised. this attack (swapping out network connection for a while to get a certificate through let's encrypt) was probably easiest/least intrusive. if it wasn't an option, the next easiest option would be taken. perhaps the options that are harder to execute are more likely to be detected, or less likely to be worthwhile.