Thanks for the suggestion, someone had just posted about this there too.
Solution that's working for me so far is this command:
cert-sync /etc/ssl/certs/ca-certificates.crt
EDIT:
This other command might also be necessary for it to be persistent but I'm not sure.
chmod -R a+rX /usr/share/.mono
Credit: https://forums.sonarr.tv/t/error-with-unable-to-connect-to-indexer-check-the-log-for-more-details/30248/10
EDIT 2:
Never mind errors came back after a while. It appears the fix I posted was related to Synology.
Edit 3:
I'm an idiot, my issues were from something is wrong with my qbit proxy, after I disabled it in sonarr everything works fine.