My husband would rather not weigh his luggage down with a dinner jacket if it is not necessary. Are they required in the fancier restaurants?

A dinner jacket? Do you mean a blazer or a black tie dinner jacket?

No!

not black tie - he's a simple guy and doesn't own one - but your basic blazer...he'll be happy to see your emphatic no Robert

Having not been yet to Lisbon cannot say but in other venues such as opera houses where some people can be very rigid about what is "correct" the dress code has been shattered. Yes, people still dress up and yes they still get pissed off because not everybody else does but the broad mix of dress now seems to be the rule rather than the exception in Europe, at least in my experience.

Men do not need jackets in most restaurants, including Lisbon restaurants. We ate in upmarket places (Cantinho do Alvillez; Sacramento) and were adequately attired without a jacket.

There may be some places in which a jacket is de rigueur but if your husband is a "simple guy" who doesn't want to pack a jacket, he's also probably uninterested in "showplace" restaurants.

My travel rule: As long as I'm wearing black or dark blue after dark, I can go almost anywhere.

Most places no. A few yes. Check before you go to anyplace upscale - or he may have to take one of their "loaner jackets" to get in.

obrigada