A possible synonym for “beyond useful” could be “exceptionally valuable”.
When we say something is “beyond useful”, we mean that it goes above and beyond what is merely useful. “Exceptionally valuable” has a similar connotation. For example, “This tool is not just useful, it’s exceptionally valuable.” It implies that the item in question has a high degree of worth that extends beyond its basic functionality.
Another synonym could be “invaluable”. This word emphasizes that something is so useful that it cannot be measured in terms of ordinary value. For instance, “Her advice was invaluable in helping me make a decision.” It shows that the advice was of such great importance that it cannot be replaced or quantified easily.
“supremely beneficial” is also a good alternative. It suggests that something is extremely beneficial to the point of being remarkable. For example, “This new technology is supremely beneficial for our industry.” It indicates that the technology offers a high level of advantage that goes beyond what is typically expected.