Hello to everyone and hats off to all of you for the great work you do to offer us such a piece of work! 
I've already installed OpenWrt on many routers for me and my friends and colleagues and now I'm looking forward to something slightly harder. I had an ancient D-Link DSL-G604T lying around (little endian mips ar7) and having no use for it anymore I wanted to use it as a wireless repeater. The stock firmware doesn't offer this possibility, OpenWrt does.
I don't know why (according to the Wiki all the versions up to Barrier Breaker should work just fine), the latest one I could get to work reliably is Backfire 10.03.1. Not an issue, it is perfectly fine for me and the intended use.
The problem is that the wireless card (a WMP-G04 ACX110) is completely unreliable at least with the driver built into the stock image (sooner or later the router hangs and wireless isn't working anyway) so I've thought to swap the wireless card (a mini-pci, quite easy and straightforward to achieve) with another (namely a BCM4306KFBG) which seems to be supported by OpenWrt.
It seems I've done my calculations in a wrong way though cause it seems that there isn't an ar7 driver for BCM43xx cards while there is one for other architectures.
Is there any way round that? I don't necessarily mean a package ready to use (I've read around there that even if the package isn't readily available in the repositories it is still possible to install the ipk just issuing opkg install address where address is exactly the address where the wanted ipk can be downloaded) but even something to compile though how to upload it to the router then? Maybe tftp or something similar but now the subject is another. I hope a solution does actually exist... Thanks in advance for your replies and a nice day to everyone!
Nothing prior to v18 is supported at this time.
Those ancient builds are, by this time, so insecure as not to be used for anything.
Devices with only 16 MB of RAM are not supportable with current Linux kernels.
First of all, thanks for your reply! I completely agree with you and I get the point indeed I'm not asking for support in the real sense of the word (should it be the case, it had been a lack of respect towards you and the other developers and this isn't absolutely the case) but just some advices on how to make a try with building something by myself. I have to add that it seems to me (but I may be well wrong) that it is more an architectural problem than one related to newer or older versions indeed it seems that the BCM43xx driver doesn't exist for ar7 even with Lede and OpenWrt 18.06. I repeat, I may be well wrong.
I also agree that a wireless repeater costs almost nothing these days and wasting even a quarter of an hour on that is a nonsense but mine is an hobby, not a work.
I also believe that, having been the DSL-G604T (and the almost only rebadged DSL-G624T after it) quite widespread, there should be quite many others lying around and maybe I'm not the only mad thinkering on this purpose (but probably yes! 
) so my hope is to help someone else on the same boat.
Have a good day!
Despite not using it as a router, having such a device connected to the internet should not be done. Wireless repeaters will be connected to the internet as well. Running that ancient software and hooking it up to the big bad internet is a disaster waiting to happen.
Even not "connected" to the Internet, the serious flaws in the 802.11 protocols would put your entire LAN at risk from anyone "strolling by".
From what I can tell, the ar7 platform is all but dead. It's still on the 4.9 kernel, apparently with nobody with interest and devices to be able to bring it forward. If someone doesn't move it to 4.19, if not 5.3, my guess is that it will be removed entirely from the next release. There's only one board supported, some kind of devel kit, perhaps, from what I can tell. The Broadcom driver depends on PCI support, which apparently that board doesn't have, so it's never built.
You can try building OpenWrt from source, if you enable support for PCI and there are drivers for board in question, it should work. However broadcom boards have the worse drivers than others.
But you can look up what driver supports the wireless board in question and see if you can add it while doing make kernel_menuconfig
having such a device connected to the internet should not be done.
I have heard that many times, but, what if only SSH service is enabled with public key authentication only? Is old version of dropbear from Blackfire vulnerable to that?
serious flaws in the 802.11 protocols would put your entire LAN at risk from anyone "strolling by".
This can be mitigated bu configuring firewall on every machine in the LAN, so that the LAN is treated as public network.
@jeff, are there any problems with 802.11 protocols if it's set to no authentification? As far as I know the flaws only allow to find the WPA2 key easily, so if there is no WPA2 key, should be no problem, right?
Unless you use WPA3 with OWE (which this ancient software won't support), your open network will have no security whatsoever. Any passerby will be open to snoop on any non-TLS / encrypted traffic happening on your LAN network. Treating your wireless network as a public network will not mitigate this. Please do yourself a favor, and do not use outdated software with known security vulnerabilities for any network related stuff.
You’re merely looking for excuses at this point, rather poorly at that. Yes, in addition to the 802.11 issues, the kernel-level vulnerabilities can’t be mitigated and dropbear and the TLS libraries both have vulnerabilities. Put a firewall on every device? LOL, that stepped past reasonable discussion into a clear sign of desperation.
Recycle it. Spend your energy finding a “project” that has tangible benefit rather than excuses.
You know how to motivate someone, I have to say! Just kidding. I understand (and underhestimated) all of the issues you're talking of here and I agree. I give up. That's a pity but still a decision necessary to take.
I'd like to thank all of you, especially, if possible, sefralgon for trying to be let's say a dreamer like I've tried to be too. The reality is another and jeff, maybe a bit harsh (but with a lot of valid reasons for that), is completely right and he deserves nothing but a plause. I apologize for starting such a useless thread though, it is clear, the intention wasn't that one.