@ebel there are free facebook and twitter clients in F-Droid (Frost, Twidere), and/or you could use Webapps (also in F-Droid) or Bromite/Fennec to just create 'apps' for these connecting to the mobile versions of those websites.
@ebel Maybe look into MicroG. Lets you use apps requiring Google Play Services without having to have Google Play Services installed. The only things which don't seem to work are actual Google-branded things like Google Maps, but Discord etc. work fine.