It is a travel router and it is currently running advanced tomato.
As your device https://openwrt.org/toh/hwdata/linksys/linksys_e2500_v3 seems to use a Broadcom wireless chip, it is unlikely that it will ever have 5 GHz support under open-source firmware, due to the lack of open-source drivers for the Broadcom wireless chips.
See, for example, https://openwrt.org/meta/infobox/broadcom_wifi
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