Well, findings so far are discovery works for these devices:
Found "Rigol Technologies,DG4062,[serial#]" on address 192.168.1.207
Found "KEYSIGHT TECHNOLOGIES,MSO-X 3024T,[serial#],07.20.2017102614" on address 192.168.1.206
Tried sending *IDN? to both - worked OK.
Captured a screenshot from the Keysight, which resulted in a png file, but when I tried to view it, I got told it was not a png.
Running the file command on it just told me it was data.
The first few bytes of the file look like this:
00000000: 470d 0a1a 0a00 0000 0d49 4844 5200 0003 G........IHDR...
00000010: 2000 0002 0008 0200 0000 f5c9 9fbd 0000 ...............
00000020: 2000 4944 4154 7801 edbd 4dac 2cdb 75df .IDATx...M.,.u.
00000030: 77ce 7df7 f123 fc92 68c1 a114 0e2c 4422 w.}..#..h....,D"
00000040: a297 c086 ded3 e01a a000 3940 3290 022a ..........9@2..*
00000050: 4311 b888 151a be9c 270c e051 8078 1a22 C.......'..Q.x."
00000060: 4090 115f 9217 27b8 8092 a108 5883 0089 @.._..'.....X...
Trying to use the Keysight 2000 plugin didn't help.
Captured a screenshot from the Rigol, which resulted in a bmp file, but when I tried to view it, I got told it had a bogus header.
Running file on it told me it was a jpeg!
Changing the file extension to jpg gave me a correct picture of the screen.