How old is your DC?
I have an almost 3 year old, in my opinion the only way to do it is to eat together wherever possible. I know it might be tricky but I would try and at least do breakfast together. Even if you just have a piece of fruit, sit together at the table. A sticker chart for good mealtimes? Set expectations beforehand (to get your sticker you need to show me how nicely you can sit at the table and eat your breakfast for example).
if my DD is not in the mood for sitting still and eating nicely at the table we basically try and distract her into it... so will give her a special job of setting the table. She will put out placemats, napkins and cutlery, and wipe the table. We also put on music sometimes (relaxing classical works wonders!) . If she has to sit and wait for us to finish our meals and she is fidgety I sometimes get out some crayons and paper like in a restaurant, or play I spy to keep her at the table.
So basically make eating at the table as nice and special as possible. You could even try some themed nights... eg making fajitas you could get DC to help you decorate the table with Mexican inspired decorations?
Also again I know it’s time consuming but if you can get DC involved in the cooking they will be more invested in everyone enjoying their food. Even if she’s only done something small, lots of comments like “mmm this pasta sauce is yummy, whoever peeled the onion must have done a really good job” or whatever.
It will take effort to start with but will become second nature!
Obviously if your DC is older you may just have to lay down the law and tell them you’re changing the habit and you’re all going to eat at the table now.
Ooh also I would try and not have the TV son right before dinner. Then you don’t have the battle of the DC not wanting it turned off. If they are helping with the cooking and then they set the table and you all go sit down it’s more of a natural progression and the TV wont be missed?
Wow that’s long. I realise these might not all work for you but just giving a few ideas that sprang to mind.