There must've been an update recently as dedicated lan servers no longer work. I used to be able to host both via the .bat method and SWBFAdmin, however now the client crashes when launching LAN. Dedicated servers are absolutely crucial due to the default TPS being 30, resulting in laggy gameplay. Servers allow you to set the TPS to 60 resulting in smooth online/lan gameplay. I can get Internet WAN servers to launch, but they do not populate on the server list. Is there a fix for these issues?

No, there is no updates.
So, to be clear, fix which one issue?

Should be a fix: contact GOG Support or SWBFAdmin author (http://github.com/jweigelt , right?).
Or both. Depend on what exactly happened.

Redownload this tool from author official github page. Stay away from old sfbfspy sites-forums - from any (one not needed and outdated, another - fake).

According to this page
http://www.reddit.com/r/battlefront2/comments/mz6evn/the_huge_importance_of_tickrate_and_multiplayer
and due to fact that author of this post is usual lamo (i judge by his text) - this is unlimited FPS CLIENT issue, not server issue.
No any game updates for no any game from no one, not matter re-\release, can fix that for 100% - every games should be played on limited FPS, just differ ways to limit and differ frames. This is one of PC gaming axioms.
According to info from PCGW, normal FPS to this game is 80 maximum. Not a 80+.

I'm the author of that reddit post. The client FPS is not the issue here, but I can't tell what you're trying to say. I have not modded for >80fps because that causes physics issues, specifically with hover vehicles. The issue here is that LAN dedicated servers no longer work, even on unmodded clients.

Was this problem ever resolved because I can't get my dedicated LAN servers to work with this game

Unfortunately I haven't found a fix, and other users have been messaging me with this same issue on reddit. This issue is so random I can only conclude a windows update broke it. The update history for this game hasn't changed since the issue started occurring so I do not know what else changed other than a windows update. Even when I had no network at all, or I try connecting to a different router, LAN still crashes when trying to launch. Here is my .bat file to launch a game. It still works just fine on pre-steam copies of the game. At this point all we can hope for is the GoG devs to take a look into the issue, but who knows if that will ever happen.

BattlefrontII.exe /lan /win /autonet dedicated /resolution 320 240 /nosound /noaim /tps 60 /gamename MyGame /playerlimit 32 /playercount 0 /bots 64 /difficulty 3 /throttle 2048 /pregametime 0 /nowait /sideselect /adminpw 12345 /spawn 3 geo1c_con 250 250

Well, Steam version got few updates (and few rollbacks). But GOG Galaxy still 1.2 multiplayer up 2.

I did test the steam version today and it seems to have the same issue. I tested a fresh install on another machine and the issue still occurs with LAN dedicated servers. Very unfortunate this functionality was removed. It was probably unintentional given you can host LAN games using the in game client. If only the tickrate could be set from within the in game client I wouldn't have such a need for a dedicated server

On a side note, I was able to start seeing my dedicated server online games. When using SWBF2Admin hosting, you must own a separate copy of the game that uses a different GOG Galaxy account, such as Steam. So I host with SWBF2Admin using the GOG copy, and join my hosted game by running the Steam copy.