Add PWA to home screen not working on chrome mobile

I recently got into front end developpement to make an interface for a nodejs server hosted on a raspberry pi. I heard of progressive web app and wanted the user to be able to install it on his phone. So here are the manifest and the service worker script. Manifest:

{
  "name": "Philips D6330",
  "short_name": "Philips D6330",
  "description": "A control app for the Philips D6330",
  "icons": [
    {
      "src": "https://192.168.1.26/cdn/favicon.png",
      "sizes": "512x512",
      "type": "image/png"
    }
  ],
  "start_url": "https://192.168.1.26",
  "display": "fullscreen",
  "orientation": "portrait",
  "theme_color": "#333333",
  "background_color": "#333333",
  "scope": "/"
}

Service Worker:

const CACHE_NAME = 'cache';
const CACHE = [
  '/',
  '/cdn/offline.html',
  '/cdn/style.css',
  '/cdn/favicon.png',
  '/cdn/linetoB.ttf',
  '/cdn/linetoL.ttf',
  '/cdn/neon.ttf',
  '/cdn/not.png',
  '/cdn/next.png',
  '/cdn/pause.png',
  '/cdn/play.png',
  '/cdn/previous.png',
  '/cdn/dots.png',
  '/cdn/rfid.png'
];

self.addEventListener('install', function(event) {
  event.waitUntil(
    caches.open(CACHE_NAME)
      .then(function(cache) {
        return cache.addAll(CACHE)
      })
      .then(self.skipWaiting())
  )
})

self.addEventListener('fetch', function(event) {
  if (event.request.mode === 'navigate') {
    event.respondWith(
      fetch(event.request)
      .catch(() => {
          return caches.open(CACHE_NAME)
          .then((cache) => {
              return cache.match('/cdn/offline.html');
          })
      })
    );
  }
  else {
    event.respondWith(
      fetch(event.request)
      .catch(() => {
        return caches.open(CACHE_NAME)
        .then((cache) => {
            return cache.match(event.request)
        })
      })
    );
  }
})

self.addEventListener('activate', function(event) {
  event.waitUntil(
    caches.keys()
      .then((keyList) => {
        return Promise.all(keyList.map((key) => {
          if (key !== CACHE_NAME) {
            console.log('[ServiceWorker] Removing old cache', key)
            return caches.delete(key)
          }
        }))
      })
      .then(() => self.clients.claim())
  )
})

I think also relevant to tell you that all of this happens on my local network so my node server uses https with a self-signed certificate made using this tutorial : https://medium.com/@tbusser/creating-a-browser-trusted-self-signed-ssl-certificate-2709ce43fd15 But even tho it's a self-signed certificate, the service worker seem to registers well on firefox and chrome, as it stores the files and displays the offline page when offline.

Here is my problem : when I want to install it from the desktop version of chrome I can but not chrome mobile (or samsung internet)... here is the piece of code i use to make it instalable :

<script  defer>
    window.addEventListener('beforeinstallprompt', (event) => {
      console.log('', 'beforeinstallprompt', event);
      // Stash the event so it can be triggered later.
      window.deferredPrompt = event;
    });

    butInstall.addEventListener('click', () => {
      console.log('', 'butInstall-clicked');
      const promptEvent = window.deferredPrompt;
      if (!promptEvent) {
        // The deferred prompt isn't available.
        return;
      }
      // Show the install prompt.
      promptEvent.prompt();
      // Log the result
      promptEvent.userChoice.then((result) => {
        console.log('', 'userChoice', result);
        // Reset the deferred prompt variable, since
        // prompt() can only be called once.
        window.deferredPrompt = null;
      });
    });

    window.addEventListener('appinstalled', (event) => {
      console.log('', 'appinstalled', event);
    });

  </script>

It comes from here https://web.dev/codelab-make-installable/

Here is a screenshot of the before install prompt event with the lighthouse report if it can help (by the way the plus sign in the url shows it's working): console log infos

But on mobile the plus sign doesn't show up and nothing happens when I click the button... And as I don't have acces to the console I can't see any errors...

------ Edit ------

After using alert to log what the console says, I think the problem comes from the service worker does register well because I get this : "ServiceWorker registration failed: SecurityError: Failed to register a ServiceWorker for scope ('https://192.168.1.26/') with script ('https://192.168.1.26/sw.js'): An SSL certificate error occurred when fetching the script.".

Is there a way to make the browser trust my self-singed certificate ?

Any help, suggestion or comment is welcome ^^