After a long time thinking about asking here I decided to try anyways. But be warned: this question is about old, never-to-be-supported hardware (5x WRT54GL ver. 1.1 & eventually, maybe 2x WRT54GL3G).
If you don't want to help with that, that's cool however saying: "just bite the bullet and buy something newer" would not be considered helpful by me. I know that already. Seriously, read it 15 times. Since I am also confused about lost wikis, forums LEDE / OpenWRT split, re-merge and new rules I hope this post won't offend anyone to an unreasonable degree... You have been warned though.
With that being said on to the issues & question at hands:
I want to reconfigure my home wireless network by using as many routers I have lying around in a productive way. Here is how it looks right now and what I would like to do, with SSID names slightly changed for privacy reasons:
Main router from ISP: Speedport W724 V type A -> notoriously artifically limited by it's shitty stock firmware...
with two Wi-Fi networks set up:
goldsteal_WLAN_Wi-Fi_4 on 2.4 GHz, Channel 1 (802.11g+n)
goldsteal_WLAN_Wi-Fi_5 on 5.0 GHz, Channels 36, 40, 44, 48 (802.11ac)
AP: WRT54GL ver. 1.1. flashed with OpenWRT "Backfire" 10.03.1 / LuCI 0.10.0 Release (0.10.0) as well as kernel 18.104.22.168 connected via LAN to the Speedport W724 V type A in order to be used as an AP:
goldsteal_WLAN_Wi-Fi_3 Channel 8 (802.11b+g)
The AP is working as intended AFAICS. Now to the hard part: I have several other WRT54GL – some of which I've already successfully set up with OpenWRT Backfire and would like to now use these to repeat the signal of goldsteal_WLAN_Wi-Fi_3. Sadly Backfire does not seem to include a bridge with the variant the WRT54GL ver. 1.1 still fully works under. Or to make it easier: I have exactly this problem: https://forum.archive.openwrt.org/viewtopic.php?id=66141.
Is there any way for me to still repeat goldsteal_WLAN_Wi-Fi_3 of the first OpenWRT router with the other 4 WRT54GLs?
Correct. Somewheres in this forum (in multiple threads), I speak of exactly the WRT54GL and this series of router. The Broadcom chips do not bridge without the proprietary WiFi drivers - not available for OpenWrt.
I have one of these routers (though not in use) and honestly, I would recommend running a Tomato build on what you have goldseal. Grab an older Shibby (or Toastman) Tomato build using the 2.4 kernel and it'll function nice and fast compared to the 2.6 and higher kernel. If you want the latest whatever it is, it'll have to be FreshTomato but it doesn't build for the 2.4 kernel. I wouldn't want to try running the current version of OpenWRT on one of these.