DATV is a thing on 430. The problem is equipment. MDARC runs DVB-S, I believe. For DVB-S, you can re-purpose satellite equipment. KH6ATV is a proponent of DVB-T (which in theory should be better than DVB-S for terrestrial paths). There is one company in Taiwan that makes DVB-T transmitters and receivers that are usable in the ham bands (available in their E-Bay store), and people have done DVB-T in the ham bands with LimeSDR. BATC has done a lot of work with DVB also. Sorry to be vague, I haven't been keeping up on my reading... about 1.5 years ago I was going to try setting up for DVB-T on 430MHz and 1.2GHz, but life got in the way.
In theory, you should be able to run 780p in a 6 MHz wide channel in the 430Hz band, or even squeeze 480i down to fit a 2MHz wide channel. (The max bandwidth allowed for amateur video in the USA on 430 is 6MHz, DVB-T does have 8MHz wide formats used in some countries for broadcast.)
For those that haven't stopped reading already:
DVB-C -- optimized for cable.
DVB-S -- optimized for satellite path loss and fading, but not for multi-path.
DVB-T -- optimized for terrestrial paths which may suffer from significant multi-path propagation.
ATSC -- The US standard, which unfortunately was standardized earlier than the rest and is expensive to generate and has outrageously poor weak-signal performance, both of which make it a ridiculously bad choice for amateur radio.
My understanding is that ATSC has fine weak-signal performance at UHF in rural areas; it's just extremely sensitive to multipath interference and it doesn't do well with the terrestrial noise in the high VHF range, so anywhere with large flat surfaces (like city buildings) is not so great.
ATSC can easily be generated with GNU Radio and any transmit capable SDR (such as the LimeSDR you mentioned). It's no worse than DVB-S as far as over the air performance. Many TV's will tune 70cm directly (cable channel 58 is 429 MHz).
GNU Radio is also capable of transmitting DVB-S, DVB-S2, DVB-T, DVB-T2 and cable TV 64QAM/256QAM. With DVB-T2, you can even send a MIMO (actually MISO) signal with dual TX SDR's.
In theory, you should be able to run 780p in a 6 MHz wide channel in the 430Hz band, or even squeeze 480i down to fit a 2MHz wide channel. (The max bandwidth allowed for amateur video in the USA on 430 is 6MHz, DVB-T does have 8MHz wide formats used in some countries for broadcast.)
Contact KH6ATV if you are interested in doing some experiments. I recommend reading his notes first: https://kh6htv.com/application-notes/
For those that haven't stopped reading already: DVB-C -- optimized for cable. DVB-S -- optimized for satellite path loss and fading, but not for multi-path. DVB-T -- optimized for terrestrial paths which may suffer from significant multi-path propagation. ATSC -- The US standard, which unfortunately was standardized earlier than the rest and is expensive to generate and has outrageously poor weak-signal performance, both of which make it a ridiculously bad choice for amateur radio.