I want to kill my NAS

I run Plex media server on my MacBook (I travel often and need it to work completely offline with no router). However my internal SSD is getting full. Rather than upgrading to the insanely expensive 8TB MacBook, I decided to compromise and allow half of my Plex library to live on a hard drive attached to my home router, meaning it should be accessible anywhere with an internet connection, but not offline.

But after two weeks of troubleshooting I can't even get the thing to work reliably over LAN. Here's where I'm at:

I use a GLI router which has a built in SMB share feature

Connecting to it via Finder fails every time (I tried every possible port/path combination)

Connecting to it via the ForkLift app fails every time

Connecting to it via MountainDuck succeeds, but any time I try to transfer a file over 1GB it gets stuck and consumes an enormous amount of CPU until I am forced to force-quit finder and start over. Plus I have to manually reconnect the drive any time I reboot or switch wifi networks. Switching to WebDav mode was unusably slow.

I have spent $40+ on Claude AI trying to fix this. It has tried dozens of ideas without success.

This isn't the first time I've had major networking problems with my MacBook. Even something as simple as connecting to a printer sometimes takes hours. And that's just with LAN. Making it accessible over WAN doubles the complexity and cuts the reliability in half.

Sure, I could spend $500 on a dedicated NAS device, but it would still be connected to the same router, and the same MacBook, with no guarantee of fewer connection issues. And it will be totally useless if I'm on an airplane with no internet.

Any ideas?