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

Opening Habpanel as below works fine (beside missing icons):

Because I use many custom icons I used to put the habpanel stuff from here:
in /etc/openhab2/html/habpanel

After copying my custom icons into the subdirectory:

I was able to use these in my static habpanel:

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

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

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).

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