Ah - there was a change to OTA release URIs some time ago, but it’s easy to change. From my notes (check the URL!):
# UPGRADE - two step (set OTA URL, then ask to download...)
mosquitto_pub -d -h BROKER_IPv4 --username 'uname' --pw "passw" -t 'cmnd/tasmotas/OTAURL' -m 'https://ota.tasmota.com/tasmota/release/tasmota.bin.gz'
mosquitto_pub -d -h BROKER_IPv4 --username 'uname' --pw "passw" -t 'cmnd/tasmotas/upgrade' -m '1'
If you have older versions, I’d read the docs, as there are intermediate firmware steps if you want to keep existing settings (personally, I’d wipe and use backlog commands on the console to configure the lot in one, but things have worked well for several upgrades once current).
# NB now use Tasmota integration so SetOption19 0
Backlog mqtthost BROKER_IPv4; mqttuser uname; mqttpassword passw; topic tasmota-9999; hostname tasmota-9999; FriendlyName Test-9999; FullTopic %prefix%/%topic%/;SetOption19 0; setoption53 1; SetOption30 0;
Moving away from HASS Discovery apparently saved a load of flash storage and memory with the complexity now in the Tasmota Binding on the server (and log-term graphing works with units as a bonus). This should mean less change in the device settings format.
More MQTT help if you need it can be found here: