grrrrrr broke again. fixed, but I just wanna post about it because it's such a stupid thing.
web host updated some system settings somewhere that makes the flask app no longer read the "utf8" charset which is what my flask's mysqldb connector is trying by default. error pointing me towards a system file Index.html about lacking 'utf' so I go look at the file and yeah I see a utf charset with alias utf-8 only (not 'utf8') so i guess that's what I gotta change
okay so lemme google about changing flask's charset setting... one answer being setting MYSQL_DATABASE_CHARSET but that doesn't work oh someone else says it's actually just MYSQL_CHARSET yay that is showing changes!......... in my error message.... now the error says utf-8 does not exist either so huh okay I guess aliases just don't actually work so I'll use the full name in my Index.xml which is utf8mb3 and bingo webpage loads up again
so the one line of code needed in my flask mysql config was just
MYSQL_CHARSET = 'utf8mb3'
and all's good again because for some annoying reason they couldn't just keep a working alias for 'utf8' which has been working for months