I diff your libcustom_Arm.so and standard library like libssl.so.1.0.2 , it seems to be a bit different to a normal library, not sure if it is related to the internal error when loading the library:
libcustom_Arm.so: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=7aac04ea29ab20ac8de64e31d9295, with debug_info, not stripped
owner@ubuntu:~$ file /opt/swi/y22-ext/sysroots/armv7a-neon-poky-linux-gnueabi/usr/lib/libssl.so.1.0.2
/opt/swi/y22-ext/sysroots/armv7a-neon-poky-linux-gnueabi/usr/lib/libssl.so.1.0.2: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=8ec623fe775f879f2a4e32cad24d38ee7bc4e71e, stripped
BTW, here has an example on how to load 3rd party library libsqlite3.so in the application, it should be similar to your situation.
You can see whether it has problem to load the 3rd party libarary.
testsql.7z (2.8 MB)
If it works, try to port your code to this application