I believe dcrwallet already supports onion HiddenServiceVersion 3, because the address for CSPP is 6i6otcms7mxhnmqf5uclj6tot4gd6dsgk3twnfefssh7v7pbqs57umqd.onion. So I had expected dcrd also supported HSv3. I attempted to set up dcrd 1.5 in bridge mode, as described in docs/configuring_tor.md. But I got the error

[WRN] SRVR: Not adding 4mcqdwmx5b5dvfl6imumomqifypwctsgneppdslw7cjwvrvrogzigtad.onion as externalip: tor host is unreachable

I am able to workaround this issue by configuring HiddenServiceVersion 2 and using that instead.