AFAIK 2.5G injectors are more common with 802.3af/at.
You could use one of those with a 48v to 24V splitter, see:
But ubiquiti injectors are said to support 2.5 Gbps even if they are marked/specced for 1 Gbps only, for what it costs I would try one of those, like: https://www.senetic.it/product/POE-24-24W-WH