Learn S/4HANA Cloud Public/Private Edition Finance effectively without a paid practice system?

I’m preparing to build practical skills in S/4HANA Cloud Public / Private Edition Finance, but a paid practice system subscription is hard to justify at the moment. I’d value your advice on how to learn effectively without one. Which free or low-cost resources do you recommend for hands-on learning (learning journeys, openSAP courses, trial or demo systems, or anything else)?