Simple Notes (also available at Playstore) should be a perfect match for you:
Simple Notes (source: Github; click images for larger variants)
It seems to match your requirements, even those not explicitly named:
- possibility to share notes: Yes, see the share icon in the first screenshot
- simple: Yes, as the name suggests
- lightweight: the
.apk
is less than 1.5 MB
- free and libre, find it at F-Droid and its source at Github (if you insist, you can also install from Playstore)
- no trackers, ads or other "PUS" (Potentially Unwanted Stuff)
For alternatives, as mentioned in my comment on your question, you can always consult my app listings – in this case the one for notes apps. There, if you're privacy aware, watch out to avoid (or at least do closely check) those entries with "monitoring icons" attached, which indicate trackers (analytics, ads etc.). Click those icons for details when investigating. Or better, only install from F-Droid :)
Enjoy!