problems around .htaccess after apache upgrade => 2.4

I recently updated apache on my server (ubuntu). Ran into a bunch of config incompatibilities. my apache conf files had some manual editing in them, so I kept them, and had to tweak some more to get apache to start and my sites to run.

I am left with the following issue: although wordpress “works” (see https://climbtothestars.org) I get an internal server error (nothing in apache logs) if I use the .htaccess file. I’ve tried playing around with the contents of the file and it seems that anything non-empty triggers the error.

I have another domain https://swissblogs.org on which I used the same .htaccess file without triggering the error. I figured I’d try installing wordpress there to see if it worked and therefore helped me advance my troubleshooting. I’m getting empty (? = blank) pages in my browser when I try to load the wordpress main page or admin, .htaccess present or not doesn’t seem to change a thing.

Ideas or suggestions for fixes or further troubleshooting? I’ve been on this for days with lots of googling and getting help from better sysadmin friends than I am, but I’m now pretty stuck!