Posted on #bitcoin-core-dev IRC channel and https://twitter.com/jonatack/status/1653086583657054217.

An attack on the I2P network is ongoing since a day or so. Bitcoin nodes running using the i2pd router (https://i2pd.readthedocs.io/en/latest/) may not be able to create SAM sessions due to floodfills. Reverting back to i2pd version 2.42.1 has been reported to be one temporary workaround. See this open discussion in the i2pd repository for updates on the attack and its mitigation: https://github.com/PurpleI2P/i2pd/discussions/1918

The Java I2P router seems to be unaffected due to its Sybil analysis and block list function. I've re-established bitcoind connections with the I2P network by switching from i2pd to the Java I2P router (https://geti2p.net).

For users who switch over: Unlike i2pd, the SAM application bridge is not enabled by default in the Java I2P Router. SAM must be started manually, or configured to start automatically, in the configure clients page in the router console or in the clients.config file.

Some links for more information about using Bitcoin over I2P: