currently I am running a GL.iNet Slate 1800ax, it is nice but not that mobile and modems did not work properly on usb port.
I found GL.iNet MUDI E750, but this one is old and has very slow speeds and no 5G.
gl.inet doesn't run openwrt, it runs their derivative.
there are very few openwrt devices with built in batteries.
AFAIK there's no battery powered 5G device supported, at all.
it'd probably be better to get something without, and use an external battery.
whatever openwrt 5G device you find, it won't be pocket size.
4G should be enough too
important is that is a bit mobile for changing locations more often
Some like netgear nighthawk series oder acer enduro connect, but with an interface that is configurable out of the box, these ones are blackboxes for users