These 3 files are the same, as of the unified builds:

• osupdate_fri3d-2024.json is the legacy file for pre 0.4.1 releases, when the device id was fri3d-2024 instead of fri3d_2024
• osupdate_fri3d_2024.json is the new file for 0.4.1 releases
• osupdate.json is the file for the waveshare_esp32_s3_touch_lcd_2

osupdate_linux-desktop.json is the legacy file for pre-0.4.1 releases, when the device ID was linux-desktop instead of linux osupdate_linux.json is for linux releases for 0.4.1 and after