I'm happy with the electronics as well. However, I do not like the software, apart from the bugs, some things are underdeveloped. This is my big disappointment considering other Siglent measuring devices I have where the firmware level is at a much better level.
For example, even such a screensaver is poorly implemented. To wake up the meter I have to press a button, it would be intuitive to press any key - but not because pressing it when the screen is off activates another function in addition to waking up (normally this pressing should be ignored and only wake up the screen). I omit other minor or major shortcomings compared to the 34465A on which Siglent heavily modeled the GUI. Because after so many years on the market, the firmware should be refined, or at least error-free.
I also have the Keysight 34465A and it's a different level but also a different price. The current price has dropped slightly, however, at the time of purchase, the SDM3065X was not available on the market. The price in companies having it in stock was much higher than the price suggested by the manufacturer (apart from the very unfavorable exchange rate of the dollar to the Polish currency, which increased the price even more).
This made me buy the SDM3065X instead of the second 34465A. Although after some consideration it has its positive sides. I wanted to completely abandon the use of a handheld multimeter at home (stationary is much more convenient). On the other hand, equipment used every day for many hours (as a multimeter is a basic work tool) can be damaged by accident / fatigue. In the case of Siglent, such an event as damage is also a "lesser loss". So Keysight stays for measurements where greater confidence is required, and Siglent for everyday use. I also have an old 34401A, but it serves more as a reserve, due to its age, it's a pity to destroy it - especially the display that burns out.
When it comes to the number of digits in a digital multimeter, it can be used in various ways. For example, my Brymen BM869S has a 50000 mode - it is even very accurate in it. However, with such a multimeter, this digit can be used to observe trends where accuracy itself is not so much required. Although here, too, Siglent and Keysight, which have charts, have a greater advantage. Yes, I can connect Brymen to a computer, but it's less convenient.
As for the references themselves, choosing them by manufacturers, etc., I will not investigate where the truth is. Both devices have their specifications in terms of how they will age in 90 days or a year and if they fit within those and I am happy with what they offer I don't care what reference voltage the manufacturer puts in.
Here, anyway, in order to conclude something, you would need to conduct reliable research with an established methodology, and not rely on a few photos from the forum to determine how important the problem may be.
On the other hand, looking at how much I paid for the SDM3065X because I managed to buy it at an attractive price, I am generally satisfied with the equipment despite many shortcomings - because basically there is nothing else on the market that can be reasonably purchased at this price.
Other Chinese brands such as Hantek, Owon, etc. I rather avoid, I do not trust this equipment. Rigol, which I used to be a fan of, also lost my trust because of bad software - I hope it won't happen with Siglent (the company will understand that in addition to the price of hardware, issues such as software quality and the speed of delivery of patches matter).