When using secondary profiles it’s better to “clone from main profile” eg. Shelter or Insular have this function, else you need to install the EXACT SAME version.
Which F-Droid version do you have installed already?
eg. for 1.15.3: https://f-droid.org/repo/org.fdroid.fdroid_1015053.apk (but you already tried I see) so you have 1.15.2: https://f-droid.org/repo/org.fdroid.fdroid_1015052.apk (I guess?)