After skipping a day (stupid IRL day job!), I started over and reinstalled everything step by step. One step I was previously not doing that I saw in another thread was to reset the path to the 'coh' folder in Island Rum ("Palm Tree" icon -> Reset Path -> select coh folder). I did that, relaunched IR, and it downloaded 28 updates. I launched the game and was able to successfully log in, but the game client crashed with a fatal exception error trying to load the point of entry zone (Founder's Falls, in my case). After quitting, when I relaunched IR it then downloaded 36 updates. Once the second update round was done, I was able to log in and play the game, 64-bit and all!
So to summarize, here are the steps that were necessary for me to get the client to a running state on my system after upgrading from the 32-bit client:
Reinstall Island Rum 082220191 or later (I'm on 082220193)
From Terminal in my user home folder, run 'rm -rf ~/.wine'
Reinstall wine ('brew reinstall wine' in terminal, and may not have been necessary, but it's a step I did)
Run 'wine cfg' in terminal; in the window that appears, click 'Done' to save defaults (again, not sure if necessary or not)
Under the Palm Tree icon:
Verify correct manifest (https://patch.savecoh.com/manifest.xml)
Click Rescan to reinstall game content
Reset Path as described above
Re-launch game client to acquire updates (28 files patched)
Re-launch game client again to acquire more updates (36 files patched)
Launch game successfully
All of that may or may not be necessary for others, but I hope it's helpful for anyone still not able to launch the game after the update.
And on a separate but related note, I would just like to say a heartfelt THANK YOU to @Manga for putting in the herculean effort on the client update. If it weren't for them, I wouldn't be playing my favorite game right now. THANK YOU!! 🤘
