As long as it's running, anyone can exfiltrate your key material from SDRAM. And even for a few minutes after it's running, if they can dump them in LN2 quickly enough. There are kludgy schemes to make this harder, like Schneier's Boojum, but in the end your attacker just needs enough resources and patience.

Most FDE schemes don't run crypto ops on the TPM itself - key derivation occurs there, then the results are cached in RAM ( or sometimes, protected CPU registers, in which case they may be able to inject privileged code into the kernel address space? ).

LUKS on a colo will probably protect you if you're a fentanyl distributor or movie pirate. Probably not if you're a terrorist or a high-value nation-state target.