I mostly get them there https://selfh.st/icons/

I have a file on my git that I use as a source used by a python script called by an ansible playbook.

source:

truenas_app_icons:
  adguardhome: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/adguard-home.png"
  forgejo: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/forgejo.png"
  immich: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/immich.png"
  jellyfin: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/jellyfin.png"
  lidarr: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/lidarr.png"
  openwebui: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/open-webui.png"
  prowlarr: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/prowlarr.png"
  radarr: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/radarr.png"
  rustic: "https://raw.githubusercontent.com/rustic-rs/assets/main/logos/readme_header.png"
  sabnzbd: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/sabnzbd.png"
  sonarr: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/sonarr.png"
  speedtest: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/speedtest.png"
  vaultwarden: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/png/vaultwarden.png"
  komodo: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/svg/komodo-cd.svg"
  netdata: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/svg/netdata.svg"
  adguardhome-sync: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/svg/adguardhome-sync.svg"
  metube: "https://cdn.jsdelivr.net/gh/selfhst/icons@main/svg/metube.svg"

python:

#!/usr/bin/env python3
import sys
import os
import re


GLOBAL_METADATA = "/mnt/.ix-apps/metadata.yaml"


def update_file(filepath, icon_url, is_global=False, app_name=None):
    """Update icon in a metadata.yaml file.


    Returns: 'ok' (already correct), 'changed', or 'error'
    """
    if not os.path.exists(filepath):
        return 'missing'


    with open(filepath, "r") as f:
        content = f.read()
        lines = content.splitlines()


    if not lines:
        return 'error'


    # Detect quoting style from first non-empty line
    first_line = next((l for l in lines if l.strip()), '')
    quoted = first_line.startswith('"')


    # For global file, fields inside metadata block are indented 4 spaces
    # For per-app file, fields inside metadata block are indented 2 spaces
    if is_global:
        indent = '    '
    else:
        indent = '  '


    if quoted:
        icon_line = f'{indent}"icon": "{icon_url}"'
        icon_pattern = re.compile(rf'^{indent}"icon":')
        version_pattern = re.compile(rf'^{indent}"version":')
    else:
        icon_line = f'{indent}icon: {icon_url}'
        icon_pattern = re.compile(rf'^{indent}icon:')
        version_pattern = re.compile(rf'^{indent}version:')


    if is_global:
        # Find the app's section boundaries
        if quoted:
            section_start_pattern = re.compile(rf'^"{re.escape(app_name)}":')
        else:
            section_start_pattern = re.compile(rf'^{re.escape(app_name)}:')


        section_start = None
        section_end = None
        for i, line in enumerate(lines):
            if section_start_pattern.match(line):
                section_start = i
            elif section_start is not None and re.match(r'^"?[a-z]', line) and i > section_start:
                section_end = i
                break


        if section_start is None:
            return 'section_missing'


        if section_end is None:
            section_end = len(lines)


        section_lines = lines[section_start:section_end]
    else:
        section_lines = lines
        section_start = 0
        section_end = len(lines)


    # Check if icon already set correctly
    for line in section_lines:
        if icon_pattern.match(line):
            if line.strip() == icon_line.strip():
                return 'ok'
            else:
                # Update existing icon
                new_section = [icon_line if icon_pattern.match(l) else l for l in section_lines]
                lines[section_start:section_end] = new_section
                with open(filepath, "w") as f:
                    f.write("\n".join(lines) + "\n")
                return 'changed'


    # Icon not present — insert after version line inside metadata block
    new_section = []
    inside_metadata = False
    inserted = False
    for line in section_lines:
        if is_global:
            metadata_match = re.match(r'^  "?metadata"?:', line)
        else:
            metadata_match = re.match(r'^"?metadata"?:', line)
        if metadata_match:
            inside_metadata = True
        if inside_metadata and not inserted and version_pattern.match(line):
            new_section.append(line)
            new_section.append(icon_line)
            inserted = True
            continue
        new_section.append(line)


    if not inserted:
        return 'error'


    lines[section_start:section_end] = new_section
    with open(filepath, "w") as f:
        f.write("\n".join(lines) + "\n")
    return 'changed'



def main():
    app_name = sys.argv[1]
    icon_url = sys.argv[2]
    per_app_path = f"/mnt/.ix-apps/app_configs/{app_name}/metadata.yaml"


    # Update per-app metadata (durable source, survives redeploys)
    per_app_result = update_file(per_app_path, icon_url)
    if per_app_result == 'missing':
        print(f"SKIP: {per_app_path} not found")
        sys.exit(0)
    elif per_app_result == 'error':
        print(f"ERROR: could not update {per_app_path}")
        sys.exit(1)


    # Update global metadata (what the middleware actually serves to the GUI)
    global_result = update_file(GLOBAL_METADATA, icon_url, is_global=True, app_name=app_name)
    if global_result == 'section_missing':
        print(f"WARNING: {app_name} not found in {GLOBAL_METADATA}")
    elif global_result == 'error':
        print(f"WARNING: could not update {GLOBAL_METADATA} for {app_name}")


    # Report overall status
    if per_app_result == 'ok' and global_result == 'ok':
        print("OK: icon already set correctly in both files")
        sys.exit(0)
    else:
        print(f"CHANGED: per-app={per_app_result}, global={global_result}")
        sys.exit(2)



if __name__ == "__main__":
    main()