i ran apt install --reinstall libffi8, restarted the system and the following messages reappeared
[ 16.874069] fail2ban-server[384]: illegal instruction (4) at 3fff7ef95970 nip 3fff7ef95970 lr 3fff7ef94f90 code 1 in libffi.so.8.1.0[3fff7ef8d000+c000]
[ 16.874154] fail2ban-server[384]: code: b1090008 f9490000 4e800020 00000000 00000000 00000000 60000000 60420000
[ 16.874176] fail2ban-server[384]: code: 81230000 712a0008 41820018 39230004 <7c004eee> 39230020 7c004fae 4bfffaf4
after rm -rf ~/libffi, git clone, autogen, this time i ran ./configure with --disable-exec-static-tramp and then copied the new libffi.so.8 to /usr/lib/powerpc64-linux-gnu/ once again restarted the system and no more messages on the console or in the logs about libfffi
# ls -l libffi*
lrwxrwxrwx 1 root root 15 Sep 28 01:22 libffi.so -> libffi.so.8.1.0
lrwxrwxrwx 1 root root 15 Feb 20 2021 libffi.so.7 -> libffi.so.7.1.0
-rw-r--r-- 1 root root 68696 Feb 20 2021 libffi.so.7.1.0
lrwxrwxrwx 1 root root 15 Sep 24 00:00 libffi.so.8 -> libffi.so.8.1.0
-rw-r--r-- 1 root root 78152 Sep 28 01:47 libffi.so.8.1.0
september 28th is the one i just compiled replacing the one contained in the libff8 package. i dont know the standard way of verifying which library is being used.