Habpanel issue (static html)

I just started from scratch based on:

Platform information:
Hardware: RPi 4 8 GB and 32 GB micro SD + zwave: Aeotec Z-Stick Gen5 (ZW090) - UZB
OS: Raspian which comes with openhabian 1.6a
Java Runtime Environment: Zulu 8 (standard openhabian)
openHAB version: 2.5.9-1 (standard openhabian)

I have copied my habpanel.config to
/var/lib/openhab2/config/org/openhab/

Opening Habpanel as below works fine (beside missing icons):
http://192.168.68.28:8080/habpanel/index.html#/

Because I use many custom icons I used to put the habpanel stuff from here:
https://openhab.jfrog.io/openhab/webapp/#/builds/openHAB2.5.x-WebUI/23/1600190676264/published%20/org.openhab.ui.bundles:org.openhab.ui.habpanel:2.5.9-SNAPSHOT
in /etc/openhab2/html/habpanel

After copying my custom icons into the subdirectory:
/etc/openhab2/html/habpanel/assets/icons

I was able to use these in my static habpanel:
http://192.168.68.28:8080/static/habpanel/index.html#/

But now I get:
Connection lost, trying to reconnect.

EDIT
I just recognized that it’s working from my (separate) PC on firefox but not on my iPhone anymore

EDIT II
I am not quite sure, but because I did not change anything, I assume the recent update of iOS caused this (at least now it’s working fine).

Question:
Is there an option to copy the custom icons somewhere else than /etc/openhab2/html where HABpanel has access to?