[Linux] Device Outputs aren't being sent from compatible cores

[SeongGino]

Description

*Specifically referring to device outputs, not display output.
Trying to use the MAME-compatible -output network equivalent option in cores like Flycast and MAME do not work in RetroArch - neither seem to be able to open the necessary port, thus no device output data is sent (e.g. for lightgun force feedback effects, LEDs, etc.)

Expected behavior

When the outputs option is enabled in a compatible core, I should be able to inspect the network traffic in localhost:8000 and see output data being sent.

Actual behavior

Port remains closed/inoperable, implying the option(s) does not even work. This DOES work in standalone MAME, implying it isn't an issue with the system (unless RA/libretro needs the user to be part of a specific group for this functionality?).

Steps to reproduce the bug

0. This issue specifically refers to Linux RetroArch, unless this also applies to Windows users
1. Install a core like Flycast or MAME (Current) and set it up as it needs to run games.
2. For Flycast, enable the "Broadcast Digital Outputs" option/for MAME, create a mame.ini in $system/mame/ini with the contents:

output network

3. Start a Naomi game in Flycast/an arcade game in MAME (like term2).
4. In a terminal, type nc -v localhost 8000
5. Observe the error localhost [127.0.0.1] 8000 (irdmi): Connection refused

Bisect Results

N/A (haven't tried other versions yet)

Version/Commit

• RetroArch: 1.16.0 (from Arch extra repository, and official AppImage release, with fresh configs)

Environment information

• OS: Arch Linux

If this issue is better spent in the individual cores' issue trackers in question, please advise - figured I'd make it a frontend issue because of how it seems to affect both trying to do the same thing.