No not a cry for help but a solution it seems and I'm a noob.
I switched from bare metal to Proxmox VM using v25 as I wanted stability while figuring it all out.
All went well and then migrated to v26 and Plex Remote Access failed.
Checked rules and nothing had changed so wondered if something had corrupted during migration, well good luck to me for working that one out.
So this morning, wiped my VM and installed v26.1.2, upgraded everything and then went about the dirty deed of getting Plex working and it just worked, so here's what I did.
Unbound DNS -> Advanced -> Private Domains -> Add
(https://i.postimg.cc/c4Pcbq6t/Screenshot-2026-02-27-154836.png)
Firewall -> NAT -> DNAT -> Add
(https://i.postimg.cc/ZndW9QmX/Screenshot-2026-02-27-160842.png)
Description= Plex Remote Access
Interface=WAN
Version=Any
Protocol=TCP
Source Address=Any
Source Port=Port
Destination Address=WAN Address
Destination Port= Single port or range 32400
Redirect Target IP=Single host or network 192.168.0.10 Plex Server
Redirect Target Port=Single port 32400
Firewall rule=Register rule
and I believe this was causing the trouble, as I had this as "PASS" and it didn't create
Firewall -> Rules -> WAN ->
(https://i.postimg.cc/cL8FxxPR/Screenshot-2026-02-27-160257.png)
corresponding entry to match the DNAT rule.
Once done, was watching movies happily on mobile phone over 5G and friends remotely at the 8Mbps allocated to each stream.