Add "Taiwan" to suggested radio settings (region presets)

[pepefrog1234]

Request

Please add Taiwan to the suggested radio settings / region presets served at
https://api.meshcore.nz/api/v1/config (config.suggested_radio_settings.entries),
which power the region dropdown in config.meshcore.io, the web flasher and map.meshcore.io.

There is currently no Taiwan entry (the nearest one is Vietnam, whose frequency does not
fit our use case). There is an active MeshCore community in Taiwan that has standardized
on a single radio config, published in our community tutorial site.

Proposed entry (matches the existing schema)

{
  "title": "Taiwan",
  "description": "920.500MHz / SF9 / BW250 / CR5",
  "frequency": "920.500",
  "spreading_factor": "9",
  "bandwidth": "250",
  "coding_rate": "5"
}

Equivalent to set radio 920.500,250,9,5.

Why these values

• Taiwan's licence-exempt LoRa allocation is only 920–925 MHz (NCC low-power RF device
  regulations; the same band used by Meshtastic's TW region and LoRaWAN AS923-1).
  920.500 MHz with 250 kHz bandwidth occupies 920.375–920.625 MHz, entirely inside the band.
• The frequency was chosen to coexist with the existing Taiwanese Meshtastic community,
  which runs on 920.125 MHz / 250 kHz — this leaves a 125 kHz guard band between the two networks.
• SF9 / BW250 / CR5 is a mid-speed configuration (~3.5 kbps) that balances range and airtime
  for Taiwan's dense urban areas and hilly terrain, and it is the setting already deployed
  on live repeaters and room servers across the island.

Context

• Community: *MeshCore TW (台灣) — https://meshcore.tw/

Note: as with #3041, the preset list appears to be served from api.meshcore.nz rather than
from a file in this repo, so this may need a config/API update rather than a code change —
happy to open a PR wherever the data actually lives if you can point me to it. Thanks!

[universebreaker]

Thank you for the proposal, but I strongly suggest not adopting this Taiwan preset at the moment. There are major concerns regarding local frequency coordination and potential RF interference in Taiwan.

1. Severe Interference with Existing Local LoRa Networks

The AS923 band in Taiwan offers a limited bandwidth of only 5MHz. Currently, the vast majority of local LoRa mesh users have already established an active network utilizing the 920.125 MHz base channel with a 250kHz bandwidth (aligning with standard medium-fast channel slots like 920.375 MHz and 920.625 MHz).

Introducing a MeshCore preset at 920.5 MHz with a 250kHz bandwidth will directly overlap and conflict with these local channel slots. This will cause mutual RF interference and disrupt the existing local LoRa ecosystem, which contradicts the goal of deploying a stable mesh network.

2. The Claimed "Consensus" is Premature and Lacks Empirical Support

While the promoter has set up a dedicated website, this proposal does not reflect a stable or widely accepted community consensus in Taiwan.

• The Reality of Node Density (1,000+ vs 13): To put things into perspective, the broader, established LoRa mesh ecosystem in Taiwan currently has over 1,000 active public nodes dynamically operating on the 920.125 MHz band. In contrast, the official MeshCore Map shows only about 13 active nodes in the entire region.
• Data Contradicts the Alignment: Crucially, even these 13 local MeshCore nodes are currently split across highly fragmented, uncoordinated frequencies (920.5, 922.5, 923.125, 924 MHz, etc.). If a true "local consensus" existed, these few nodes would already be aligned on the proposed 920.5 MHz preset, which is clearly not the case.
• No Active Community Backbone: This proposal relies entirely on a single managed page. It lacks the backing of active public discussion forums and chat groups, or collaborative radio test logs with substantial local user engagement. MeshCore in Taiwan is still in an early, individual experimentation phase.

Recommendation

To protect the local radio environment and prevent uncoordinated channel fragmentation, we should leave the Taiwan configuration as it currently is.

The AS923 band in Taiwan is already heavily constrained with only 5MHz of total bandwidth. Hard-coding an official preset based on unverified data will permanently fragment the limited spectrum. Even with a theoretical 125kHz guard band, squeezing a 250kHz bandwidth channel into this specific slot risks mutual adjacent-channel degradation and restricts future network scalability for both user bases. Local users need more time to conduct thorough radio testing and organically develop a genuine consensus.