Process identifier is what we’re talking about here. Do you have any convenient graphical tool to see what PID Docker is running as? If not, you likely have ps. Possibly you also have pgrep which avoids possible work of using ps with grep.
Example with duplicati because I don’t have anything docker here to document:
$ pgrep duplicati
140982
$ ps -e | grep duplicati
140982 pts/9 00:05:29 duplicati
$ file /proc/140982/exe
/proc/140982/exe: symbolic link to /usr/lib/duplicati/duplicati
$ file -L /proc/140982/exe
/proc/140982/exe: ELF 64-bit LSB pie executable, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32, BuildID[sha1]=c098aa1274509775f35a0d3df765293bd91f4640, stripped
$
I suppose you could survey some likely OMV-provided files such as ps for bitness. Most are probably in /bin or /usr/bin, and file can just use their path directly.
I’m not sure why you got a 32 bit docker. I’m not sure how well it runs 64 bit images. Researching the latter didn’t work well. You need 64 bit CPU, but I think you have it.