While I currently use kubuntu for my daily driver, I wouldn't use it for a web server or anything that I was concerned about leaking data to third parties.
For Bitcoin and secure crypto transactions, I would look into Manjaro or any Arch distribution powerful enough to handle the necessary software.
Linux has desktop and server OS, while you can use desktop OS for the webserver it is recommended to use server OS for web servers, more likely to use minimal iso image for that since you will only need to run what is needed for the web servers,
Linux flavors are safe, if they have been compromised it means you messed up the configuration firewall and permissions.