Worth noting that it is physically impossible for current flat panel displays to have full coverage of rec.2020, because the spectral width of each primary is too wide with current flat display tech (LED, LCD, etc.)

Full rec.2020 coverage requires the use of lasers, so you can get a ~spectrally pure primary.

My prediction is that the next big move in display tech after 8K will be a transition from LCD/LED to VCSELs or some other teeny laser pixel, so they can advertise full rec.2020 coverage.

After that, maybe tunable quantum dot lasers so they can get full CIE 1931 coverage, but that's probably at least 15-20 years away.

On the other hand, for viewing images on monitors, Adobe RGB is not a desirable color space. The worst primary color of PAL/SECAM and of the closely related SMPTE C and Rec. 709 color spaces is the primary red color.

While in the blue and green regions the colors that are not representable in PAL/SECAM/SMPTE C/Rec. 709 can be represented by reducing their saturation, in the red corner, from purple to yellow, besides colors that can be represented by reducing their saturation there are also colors that can be represented only by reducing both their saturation and their brightness.

Moreover, in the red corner, from yellow to purple, there are many frequently encountered objects with such saturated and bright colors, e.g. flowers, fruits and clothes.

So the really noticeable improvement in color reproduction on monitors is when passing from PAL/SECAM/SMPTE C/Rec. 709/Adobe RGB to monitors with DCI-P3 primary colors.

DCI-P3 keeps the primary blue of PAL/SECAM, but it has much better primary red and primary green colors. The green is not as good as that of Adobe RGB, but the better red provides a much more visible improvement.

Many relatively cheap monitors, e.g. all my Dell monitors, have a menu option to replace the default sRGB color space with the "DCI-P3" color space (and they can display almost 100% of the DCI-P3 color gamut). On any such monitors, by "DCI-P3" is meant the Apple Display P3 color space, i.e. DCI-P3 primary colors combined with the PAL/SECAM D65 white and with the sRGB non-linear transfer function.

In cheap monitors, the DCI-P3 color gamut with 10 bit per color component is the best that can be found. The monitors whose color gamut is a larger fraction of the Rec. 2020 color space are expensive, because they normally must use quantum dots or OLED or both.

Nevertheless, as the output color space for any high-quality photograph, the Rec. 2020 color space is preferable, even if most people who would look at the photograph now would clip its color gamut to the sRGB or DCI-P3 of their monitors. However those who have better monitors, whose numbers will be increasing in the future, will be able to see any color that can be displayed by their monitors, without having the quality of the photograph already degraded by whoever has processed it.