You can build the image yourself, but have to switch off some packages or features - otherwise the image (linux-kernel + tools) is just too large or consumes too much memory. The original router has 8 megabytes RAM-memory and 2 Megabytes flash ("storage"). You can boot a recent kernel 6.16.5, but with 8mb there is not much left to work with 8-)

A starter is here: https://intercity-vpn.de/files/openwrt/wrt54gtest/minimal/

I remember swapping the TSOP packages on a WRT54 to double the RAM.

Here's a blog post about this, not sure if it was the same one I followed:

https://blog.thelifeofkenneth.com/2010/09/upgrading-ram-in-w...