21.05.2 is old. You should upgrade.
However I'm not aware of anything that would specifically affect OpenVPN speed in that version.
In 22.05 you can use QAT and DCO which can be significantly faster. However 25Mbps is far below what the 5100 is capable of in any config.
What sort of latency is there across the tunnel from the laptop?
High latency and SMB, especially if it's V2, is notoriously terrible.
Try testing with something else to be sure it's not just the link, like iperf or example.
Steve