Upgrading to Tasmota 7.1.2 I encountered a few issues and was unable to compile with the Arduino IDE.
The quick workaround was to upload tasmota.bin using the esptool.py method as this copies the binary straight to the MCU without any compilation, of course. Got the WemosD1mini running and was able to customise (WiFi and MQTT) it as usual with its web server and do further fine tuning on the console (such as static IP address using the IPAddress1 xx.xx.xx.xx command in the console).
Going back to the Arduino IDE, a clue was given in the first error messages about the ArduinoJson library. It turns out that Tasmota7.1.2 will give error if you are using the ArduinoJson6x library. I simply deleted that version from the Documents/Arduino/Library folder, copied & pasted in its place the ArduinoJson5.13.4 that is including in the tasmota zip package and voila! It runs.