hey even i am facing the same problem, ya its true that some rom has messed with my modem files also but when i flash the stock rom even still am unable to connect to internet,
could i be provided with modem tar file pls so that i can reset it completely
PLEASE NOTE: I am not a professional/developer. In fact I am new to XDA. I just came here to get an upgrade for my phone, and I was not disappointed

.Therefore, all I state is based solely on my personal experience.
So, before doing what I stated in my post, I tried to flash just the "modem.bin" file from my stock J500F ROM using Odin. Unfortunately, it did not fix the problem.
By the way, do you have the stock ROM (the original Samsung Touchwiz ROM) for your phone? If yes, you can extract the files you need(including modem.bin) from the stock ROM using 7zip.
Also, be aware that for some reason, you won't be able to flash the modem file using the latest version of Odin. I had to use Odin 3.07 to flash mine and could not flash it using Odin 3.14.1.
Further, I can give the files to you but please make sure your phone is the same model as mine(J500F) before flashing. If not, you will have to find the stock firmware for your model and extract modem from that. However, as I said, flashing just the modem did not work for me (it might just work for you though

).
If you want me to share the files nonetheless, would you like me to e-mail the files to you? Send me a message about it.
Also, if this doesn't work, do what I did. Wipe Dalvik/ART Cache, Data, Internal Storage, Cache, System from recovery, also wipe the modem. Now flash the Stock ROM. Check if Mobile Data works and please note your APN settings if it works. Now, if it works, flash Lineage OS again, and enter your APN settings.
By the way, are you saying that for you, Mobile Data doesn't work EVEN ON THE STOCK ROM?