I personally do not eat in the meat restaurant that have a hashgachah but are open on Shabbat. My father (not observant) is insistent we go to his favourite nyc deli when we visit manhattan next. Are there any circumstances under which eating in such a restaurant would be halachically permissible? I understand that a generation or two ago when there were many less kosher options frum folks would frequent such places on Wednesdays or Thursdays. Any advice here would be most welcome - thanks!
You can only eat in a restaurant that has a good Hashgacha or a Shomer Shabbos owner. There are some restaurants that are open on Shabbos and have a good Hashgacha. I’m not sure how they handle the many issues that would arise.
My father would always say its better to go to a non-kosher eatery and just get fruit, vegetables (w/o bugs), drinks, etc. The reason being that if someone saw you in there eating, they would know that you’re only eating something kosher. However, in a weak Hashgacha eatery, they may assume you consider it to be kosher and follow your lead, not realizing that you’re only eating and not realizing that you’re only eating fruit, vegetables (w/o bugs), drinks, etc.
I hope this makes you more at ease