Mullvad has a 30-day money back guarantee.
Apart from that, some payment methods (like crypto) allow transmitting arbitrary amounts. At least, paying for years in advance works without issue. You could pay a few cents and try it out, but be mindful of fees.
Almost all extensions will weaken your security posture. In fact off the top of my head there are basically only two kinds of extensions that could improve it:
Anything else is questionable at best. Maybe you could create browser profiles where you install extensions somewhat more liberally, with decreased expectation of safety.
Like basically all cloud providers, Oracle publish their public-facing IP address ranges.
https://docs.oracle.com/en-us/iaas/Content/General/Concepts/addressranges.htm
Many services block these because, as you are pointing out, standing up VPN tunnel routing on a cloud instance is sort of trivial. Cloud providers publish these ranges specifically so anyone can block them easily. If lemmy.world is not blocking Oracle Cloud already, it’s only because they just haven’t come around to it.