Thanks for such a useful app!
I connected my Thunderbird with two official French calendars available with ICS and I wanted to get access to them on my Android phone also. When I tried to connect using ICSx5 I got an issue for one of them.
The ICS sources are available here : https://www.data.gouv.fr/fr/datasets/le-calendrier-scolaire/ and the links I tried to use are https://fr.ftp.opendatasoft.com/openscol/fr-en-calendrier-scolaire/Zone-B.ics and https://www.data.gouv.fr/fr/datasets/r/c03b7373-6698-4e44-b5f1-9408b4b2cfe8 (seems to be a redirection).
With both links I get the following error:
Attempt to read from field 'sun.util.calendar.BaseCalendar$Date java.util.Date.cdate' on a null object reference
I successfully connected another calendar provided by the same site (see https://www.data.gouv.fr/fr/datasets/jours-feries-en-france/) : https://etalab.github.io/jours-feries-france-data/ics/jours_feries_metropole.ics
ICSx5 version : 1.9.3 from Fdroid.
Android 11 with Samsung One UI 3.1, Kernel 4.14.113-21578199
Thanks in advance to have a look.