RHCS: ceph-mon upgrade to 5.x fails with "unable to decode FSMap: void FSMap::decode"

Issue

During the upgrade from "14.2.22-128.el8cp" to "16.2.10-172.el8cp" without MDS the ceph-mon fails with:

    -2> 2023-06-19T11:31:26.208+0200 7f8f283c0880  5 mon.mons-0@-1(???).mds e0 Unable to load 'last_metadata'
    -1> 2023-06-19T11:31:26.208+0200 7f8f283c0880 -1 mon.mons-0@-1(???).mds e0 unable to decode FSMap: void FSMap::decode(ceph::buffer::v15_2_0::list::const_iterator&) no longer understand old encoding version v < 7: Malformed input
     0> 2023-06-19T11:31:26.210+0200 7f8f283c0880 -1 *** Caught signal (Aborted) **
 in thread 7f8f283c0880 thread_name:ceph-mon

 ceph version 16.2.10-172.el8cp (00a157ecd158911ece116ae43095de793ed9f389) pacific (stable)
 1: /lib64/libpthread.so.0(+0x12cf0) [0x7f8f1d26ccf0]
 2: gsignal()
 3: abort()
 4: /lib64/libstdc++.so.6(+0x9009b) [0x7f8f1c88209b]
 5: /lib64/libstdc++.so.6(+0x9653c) [0x7f8f1c88853c]
 6: /lib64/libstdc++.so.6(+0x96597) [0x7f8f1c888597]
 7: __cxa_rethrow()
 8: /usr/bin/ceph-mon(+0x233a76) [0x55d76c8dfa76]
 9: (PaxosService::refresh(bool*)+0x10e) [0x55d76cab322e]
 10: (Monitor::refresh_from_paxos(bool*)+0x18c) [0x55d76c95d16c]
 11: (Monitor::init_paxos()+0x10c) [0x55d76c95d47c]
 12: (Monitor::preinit()+0xd30) [0x55d76c98b470]
 13: main()
 14: __libc_start_main()
 15: _start()