To prep for downgrading, I modified 
pacman.conf and added linux and systemd subsystems as Ignores (no point upgrading them at this point), and added an commented-out entries for 
python et al and for 
certbot.
I backed up the current mirrorlist and changed the entry to point to 
http://tardis.tiny-vps.com/aarm/repos/2021/11/30/I then ran a downgrade: 
$this->bbcode_second_pass_code('', 'pacman -Suuyy')
A couple of errors came up (had to run it a couple of times) regarding pre-existing files - these were symlinks for libraries - I deleted them, and the upgrade completed, and 
certbot worked  
 
 I edited pacman.conf and uncommented the the ignores for 
python and 
certbot, then restored the mirrorlist and ran a regular $this->bbcode_second_pass_code('', 'pacman -Syu'). Ran $this->bbcode_second_pass_code('', 'certbot renew --dry-run') successfully and then the actual $this->bbcode_second_pass_code('', 'certbot renew')
Now to reboot!
Thank you 
moonman for that suggestion!