It seems that the Siglent SDS1000 comes in four flavours:
SDS1000CFL: 4 channels, 70..300 MHz, 2 GSa/s, 24 Kpts memory depth
SDS1000CM: 2 channels, 60..150 MHz, 1 GSa/s, 2 Mpts memory depth
SDS1000D: 2 channels, 25..200 MHz, 500 MSa/s, 32 Kpts memory depth
SDS1000C: 2 channels, 25 MHz, 500 MSa/s, 4 Kpts/ch memory depth
Older nearly obsolete models With 5.7" TFT have been long time. (SDS1000C,D,CM etc)
No one know who come first but in western markets Rigol come very popular fast. Maybe due to more marketing work in western countries and example with this "Purposely designed for hack". If look Rigol and Siglent they looks like same - nearly all bicycles looks like same. Maybe they also copy each others becouse all these have 2.... etc. If human do not copy and learn from each others we still live in caves.
If look deeper to PCB, there are lot of similarities but also then lot lot of differencies in details. It mean that they are not directly copied with Xerox copy machine.
But principle is same, and also this Rigol front end what is not at all Rigol design, it is copycat from Tektronix but still also many differencies in details. (before years I have also tested and looked Rigols)
Rigol have not developed this front end principle, it is nearly as common public principle (all can free use it) and it can find in most this class of oscilloscopes and also it design principles can find in public textbooks - there is not ANY secrets and no one own this circuit principle. Some one select 499 ohm resistor and someone use 511 oh.. some use 33pF capacitor and some other use 27pF also components can add or subtract and positioned and routed different and it is not then copy.. then who copy who. But sometimes it is fun becouse they copycat also errors, mistakes.
Also these kind of things best design help sources are component manufacturers application notes - who read these. And if really want study and learn there are old Hewlett-Packard journals. Very very pity this whole company have destroyed after Hewlett and Packard. Agilent - everyone can do these cheap chinese boxes - even chinese but China is going too expensive country for cheap mass production.
There was some old case in China where Atten and Rigol go to court. I do not know exactly what this case include and what was exactly result. There are some words that Rigol win but what it include exactly is not clear for me.
(And some side note:
Atten do not have oscilloscope product line in Atten factory! Atten use OEM manufacturers afaik. Who all do scopes for Atten and with what Atten "standards" this I do not know. One OEM manufacturer is Siglent but who knows who others do sub manufacturing also for save money. But all know that it is possible (with big lots) use buyer "standards" for exacmple save some money.)
Siglent is big ODM and ODM manufacturer. I do have any proofments who all use Siglent factory for they "own" products. You can buy all without any sign about Siglent name.. even PCB's may have your name.. it is only question about money. I have not any proofments that they do also for Rigol. It is so complex system of small sub manufacturers, OEM ODM manufacturers and cross manufacturing in China that maybe only a mountain troll know truth.
Siglent product list afaik:
(There is also old 5.7" TFT models but it is other case and it can simply regognize becouse they do not have last letter L)
All these "new" have 7" TFT
SDS1000DL 2 channel only, 25 - 200MHz all in this serie 500MSa/s 32k sampling buffer
SDS1000CNL 2 channel only, 70 - 200MHz this serie is 1GSa/s (exept 200MHz model have 2 x 1GSa/s (but not 2GSa/s max)) 40k sampling buffer exept 200MHz model 5k sampling buffer.
SDS1000CML 2 channel only, 70 - 150MHz only this serie (3 models) have 2M half speed long memory) all have 1GSa/s max 2M half speed sampling buffer
SDS1000CFL 2 and 4 channel, 70 - 300MHz all in this serie 2GSa/s 24k sampling buffer.
CNL/CML factory claim is max 2000wfms/s.
For slow speed there is in some models 6Msample continuous recording memory (and with extremely low speed there can record directly to USB stic).
(do not mix with frame recorder what is not continuous (lack of data between frames), this have max 2500 lenght )
Images quality are poor, sorry. Purpose was only to tell the general picture of what kind of structure.
Also I do not know anything about original source of these images. But these pictures approached from the east and landed to my area without asking landing permission.
And this is not "new" unprecedented and progressive cross-breaking model, no one do not try claim it.
It is simple entry level and economy model without any big advantages. But still many also nice features in FW and building quality is not cheapest crap.
But as all chinese, FW is not perfectly finished and there are many minor things what can do better. (but also big names have learn this from chinese and they have also started more ans more loose work.. look some agilent etc things. If these fails and errors happend 1980 or 1990 they need call back every equipment to factory - it is really BIG shame these old times good companies have started this copmpetition with prices and maybe also competite who can do most crap what still can sell only using old brand name. How long they can keep this name..)
Signal quality is just what can expect from this construction. It can do better but then its price is littlebit different. Small amount of more lab work and some components more and some changes and some minor differencies in PCB routing etc..
It is just as one screw driver and you can see these hundreds of different cheap names. All these can turn screw when hobbyist do one table or fix his chair. All peoples do not need Stahlwille tools.
All these same kind of oscilloscopes can show blinking led voltage changes "image" and other fun things.
Just if you like Rigol, buy rigol, if like UNI-T just buy it. There is not most bad and not most good. One have one thing good other have other good. There is not all good perfect equipment in this price class. All depend how You weight different things, pros and cons and also your feelings.
I have seen real crap manufactured things. This is not at all this kind of product.
Also there can see they have not try save every jiao what is possible.
EDIT: there was "tinhead" explanation about some things what I did not know. tnx.