https://linuxupskillchallenge.org/00/
A month-long course aimed at those who aspire to get Linux-related jobs in the industry - junior Linux sysadmin, DevOps-related work, and similar. Learn the skills required to sysadmin a remote Linux server from the commandline.
Oracle suck, and the omission of Oracle Cloud Infrastructure may be intentional here, but they offer 2 indefinitely free servers which only required a linked card iirc. Could be worth adding to the list?
If you sign up for a PAYG account (which requires a $100 charge to your card, which is then refunded), you can actually get he ARM servers they advertise as always free. They’re a bit beefier (4 Ampere cores, 24gb ram).
And they give 200gb of storage you divvy up between your instances.
But Oracle deeply suck as a company, so maybe not mentioning them is the right choise