If you put imnage to footnoter in Calc and save file and you restart LO, nothing happened - image is out. It disappears.
So Calc don't preserve image content in footnoter.
Hi @Petr, thanks for reporting.
Version: 18.104.22.168 (x64) Build id: f79b5ba13f5e6cbad23f8038060e556217e66632
Last version working for me:
Version: 22.214.171.124.0+ Build ID: 1fc1d0d7d38bb16832d0d78d78682ed2d5f8716f
*** This bug has been marked as a duplicate of bug 89245 ***