Sentry's documentation for setting up capacitor projects is a bit outdated for Capacitor 3.
As seen here, Capacitor officially recommends using automatic plugin loading on android. I bumped into a couple issues when using the provided add(SentryCapacitor.class) approach where then a few other plugins no longer worked. Switching to the registerPlugin approach fixed this for me.
This callout may be worth adding to your docs, as Cap2 vs Cap3 setup.