Both MQTT Connector and MQTT Shims plugins have been updated for Indigo 2022.1 and should be available in the plugin store.
In addition, the MQTT Broker plugin is new for Indigo 2022.1 and will be available in the store shortly. This plugin implements a simple MQTT broker and can be used instead of Mosquitto. This plugin is only suitable for use when all MQTT clients are on your local LAN, as there is no authentication enabled at this time. I do NOT recommend port-forwarding to this MQTT broker from outside your LAN. No configuration is necessary. It will use the default MQTT port unless overridden in the plugin config.