Alan,
FWIW, working primarily with Lazarus on OSX here, as you did, I did quite a bit of searching on the forum and across the net, to learn about the multiply_defined and the version warnings --with almost nothing to be found.
From my history, linker failures (as Lazarus reports these) can be a very consequential event, In this case, the newer apple linker produced these linker warnings on my wife's up to date M1 Macbook pro but not on my older 2015 machine.
Anyway, it seems these options are being passed incorrectly to the Apple linker by Lazarus and are bugs which need to be addressed, though probably not urgently. No effect I can find at on our big multi-threaded L projects!