I mean any cloud is trivial to secure if you just use strong encryption on anything you put on it.
Now, before you say "I don't do anything illegal so it doesn't matter, I'm only worried about corporations" think for a minute about how often companies do have ties (even informal ones -like friends) with people who work in agencies with those resources. You still run the very real and likely risk of a quid-pro-quo ("hey, if you can give us a way to peek into these encrypted drives we'll leave the listings out for you /wink").
In the year of Our Lord 2022 I really would not trust cloud encryption -strong or otherwise; at least not for me personally and my personal/hobby data. If I was working for a company that has a legal department with teeth behind me and I was storing things on the cloud for them? That would be a different ballgame.
Any modern symmetric encryption is extremely likely to be safe against state-level actors for the observable future assuming your encryption key is not compromised and has enough entropy in it. Even with quantum computers you only need twice longer keys. Roughly, AES-256 would provide AES-128 level of security in the presence of practical quantum computers.
If you feel especially paranoid about potential backdoors in algorithms, you can chain several algorithms from different organizations (e.g. AES, Kuznyechik, ChaCha20, and SM4) initialized with different keys. Though such practice is frowned upon by cryptographers.
Yes. AES-256.
One-Time Pads as well, but of course then you have the problem of how to securely store the pad.