[BUG] Chinese characters render as squares when system locale is Chinese (Simplified) — unaffected when set to English (US)

[Sycxp]

Please confirm these before moving forward

• I have searched for my issue and have not found a work-in-progress/duplicate/resolved issue.
• I have tested that this issue has not been fixed in the latest (beta or stable) release.
• I have checked the FAQ section for solutions.
• This issue is about a bug (if it is not, please use the correct template).

UniGetUI Version

2026.2.7

Windows version, edition, and architecture

Windows 11 Pro Insider Preview Build 26300 (10.0.26300.9032) x64

Describe your issue

English:
When the system display language is set to Chinese (Simplified, China), almost all Chinese characters in the UniGetUI interface (including package names, descriptions, and UI labels) are rendered as empty squares (tofu/□□).
However, when I change the system display language to English (United States), the exact same program shows all Chinese characters correctly (package names like “微信” are readable).

This issue is not related to MacType (I tested on a clean system without MacType). It also persists regardless of the system default font — even after restoring to Microsoft YaHei UI or using a custom font SDK_SC_Web (which covers full CJK).

I have tried nearly all common workarounds (listed below) but none resolve it. The problem appears to be intrinsic to Avalonia UI’s font fallback behavior on Windows with Chinese locale.

中文：
当系统显示语言设置为中文（简体，中国） 时，UniGetUI 界面中的几乎所有中文字符（包括包名、描述、UI标签）都显示为空方块（豆腐块/□□）。
但是，当我把系统显示语言切换为英语（美国） 时，同样的程序所有中文字符显示正常（例如“微信”“百度网盘”等包名均可读）。

此问题与 MacType 无关（我在没有 MacType 的干净系统上测试过）。它也不因系统默认字体而改变——即使恢复为 Microsoft YaHei UI 或使用自定义全 CJK 字体 SDK_SC_Web，问题依然存在。
我已尝试几乎所有常见的解决方案（见下文），均无效。该问题似乎源于 Avalonia UI 框架在 Windows 中文区域下的字体回退机制缺陷。

Steps to reproduce the issue

English:

1. Set Windows display language to Chinese (Simplified, China) via Settings → Time & Language → Language & region.
2. Restart the computer (to apply system-wide changes).
3. Launch UniGetUI (version 2026.2.7).
4. Observe any Chinese text in the main window (e.g., installed package list, discovery page, or settings).
5. (Optional) Change display language back to English (United States), restart, and observe that Chinese characters now render correctly.

中文：

1. 通过“设置 → 时间和语言 → 语言和区域”将 Windows 显示语言设为中文（简体，中国）。
2. 重启计算机（使系统级更改生效）。
3. 启动 UniGetUI（版本 2026.2.7）。
4. 观察主窗口中的任何中文文本（如已安装包列表、发现页或设置项）。
5. （可选）将显示语言改回英语（美国），重启后观察中文现在显示正常。

UniGetUI Logs.txt

UniGetUI Log

`N/A – I was unable to capture meaningful logs; the console output shows no font-related errors. I am willing to provide logs upon request with specific debugging flags.`

I hava upload my available logs.

Package Managers Logs

`N/A – The issue is purely UI-rendering, not related to package manager operations.`

Relevant information

English:

• UI Framework: UniGetUI migrated from WinUI3 to Avalonia (this issue likely resides in Avalonia’s font fallback chain).
• System locale: Chinese (Simplified, China) — also tried enabling/disabling “Beta: Use Unicode UTF-8 for worldwide language support” (no effect).
• Fonts tested(Using NoMeiryoUI):
  • Default Microsoft YaHei UI
  • Custom SDK_SC_Web (extracted from Genshin Impact, full CJK, modified to declare Simplified Chinese support)
• Workarounds attempted (all failed):
  • Deleting Avalonia font cache (%LOCALAPPDATA%\Avalonia\FontCache and %TEMP%\Avalonia – these folders did not exist).
  • Modifying Windows registry FontLink\SystemLink to add Microsoft YaHei UI and SDK_SC_Web as primary fallback for Segoe UI.
  • Restoring system default font to Microsoft YaHei UI.
  • Disabling the “UTF-8 beta” and restarting.
• Key observation: The problem only occurs when system language is Chinese; switching to English (US) immediately fixes it, which strongly suggests the issue is not font-specific but locale-dependent in Avalonia’s rendering pipeline.
• This issue was previously reported by me in **Issue [BUG] UniGetUI has a bad adaption for Chinese when using a Japanese font #4786 ** (half a year ago) but received no response. I am reopening with updated info.

中文：

• UI 框架：UniGetUI 已从 WinUI3 迁移到 Avalonia（此问题很可能源于 Avalonia 的字体回退链）。
• 系统区域：中文（简体，中国）—— 已尝试启用/禁用“Beta: 使用 Unicode UTF-8 提供全球语言支持”（无效果）。
• 测试过的字体（通过使用NoMeiryoUI修改）：
  • 默认 Microsoft YaHei UI
  • 自定义 SDK_SC_Web（从《原神》提取，完整 CJK，已修改为声明简体中文支持）
• 已尝试的解决方案（均无效）：
  • 删除 Avalonia 字体缓存（%LOCALAPPDATA%\Avalonia\FontCache 和 %TEMP%\Avalonia – 这些目录不存在）。
  • 修改 Windows 注册表 FontLink\SystemLink，为 Segoe UI 添加 Microsoft YaHei UI 和 SDK_SC_Web 作为首选回退字体。
  • 将系统默认字体恢复为 Microsoft YaHei UI。
  • 关闭“UTF-8 Beta”支持并重启。
• 关键发现：问题仅在系统语言为中文时出现；切换为英语（美国）后立即恢复正常，强烈表明问题并非字体本身，而是 Avalonia 渲染管道中与区域相关的行为。
• 此问题半年前由我报告过（Issue [BUG] UniGetUI has a bad adaption for Chinese when using a Japanese font #4786 ），当时无人回应。现以更新信息重新提交。

Screenshots and videos

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