You can use the --version flag
$ trytond --version
trytond 5.4.2
You can use the --version flag
$ trytond --version
trytond 5.4.2
I should have mentioned that my tryton lives in a docker container… ):
Then try:
$ sudo docker run --rm tryton/tryton trytond --version
            Thank you very much indeed.
In the end, I could make the GTK client work, with help of this thread