A fellow countryman of yours, @dBC, has contributed a lot about these sensors very recently, perhaps he can advise?
Meanwhile, you might like to look at this: Ds18b20 and emonTX3CM firmware
Whether the emonTx would “just work” depends on the sketch that you’re running. I haven’t got enough sensors to test the latest CM sketch, I think that’s why it’s set to accept 3 only. The earlier ‘discrete sample’ sketch (which works in a completely different way, and if you’ve had your emonTx’s since before mid-October 2019 will be what you use) accepts 6 by default.
But one caveat: the power available to the emonTx from the a.c. adapter is limited by design, so you probably will need a 5 V d.c. USB power supply for that one.
Also note that the power to the sensors using the screw terminals is switched, for those using the RJ45, it isn’t.