The switch http⬄https only works after adding the solider.sldc.pl site to the exceptions list. Click to copy link to clipboard.

Chrome
   chrome://settings/content/insecureContent ⇨ Display of unsecured content has been allowed ⇨ Add ⇨ [*.]solider.sldc.pl
Firefox
   Click the shield icon located to the left of the address bar. Then click "Secure connection" (next to the padlock icon) and select either "Off" or "Off temporarily".
Opera
   opera://settings/content/insecureContent ⇨ Display of unsecured content has been allowed ⇨ Add ⇨ [*.]solider.sldc.pl
Edge
   edge://settings/content/insecureContent ⇨ Displaying unsecured content is permitted ⇨ Add ⇨ solider.sldc.pl