Before update, your /usr/NX/etc/ lic files should look like this:
If I dpkg install the .deb installer, I see no backup files listed:
blah@raven-5820:~$ ls -l /usr/NX/etc/*lic*
-r-------- 1 nx root 876 Oct 7 2021 /usr/NX/etc/node.lic
-r-------- 1 nx root 809 Oct 7 2021 /usr/NX/etc/server.lic
blah@raven-5820:~$ sudo grep "Product Id" /usr/NX/etc/*lic*
/usr/NX/etc/node.lic:Product Id: LEDSN
/usr/NX/etc/server.lic:Product Id: LEDS
Is this unexpected?