~~Requires shared volumes (or a single container with every single microservice)~~ Actually could still be possible

The only issue with Sentry, which I've considered self-hosting, are the hefty CPU & RAM requirements. I haven't looked into it too deeply, but the cut off did seem a bit steep. Their free plan is surprisingly generous.

After a more detailed look, this may violate the FSL for Sentry (https://fsl.software/).

I don't think it violates anything, since the intention of hosting an instance here should be for personal/single use. It would violate if you hosted it here and tried to sell it as a completely new service to third parties.