Iperf3 is solved, but is only temporary, because if I exit from the terminal, path and library path is resetted to the original.That is an inherent limitation of OEM firmware, and why many turn to third-party firmware, where these features are more common, either directly or indirectly via Entware. But that assumes your router even has a third-party option, which I'm unaware of for the RT-AX52 (doesn't mean it doesn't exist, I'm just unaware of it). It's why you're wise to consider whether third-party support is available when choosing any router.
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