Edit: I'm still working on our travel list, but have been looking into this subject a lot lately. So I'm replacing the original post I made about this subject early on with my current list of countries I'm going to (or still researching), in case anyone else finds this list of places we like useful

To me/us personally, the Caribbean nations look the best, and happens to also be one of the best regions for having many nations that allow multiple passports and dual citizenship.
This is my personal list of Caribbean countries I'm most interested in traveling to to get a feel for, and then look into their rules on residency/citizenship:
Antigua and Barbuda
Barbados
Dominica
Dominican Republic
Grenada
Jamaica
Montserrat
Saint Kitts and Nevis
Saint Lucia
Saint Vincent and Grenadines
Take my initial research about which nations allow multiple passports / dual citizenship with a grain of salt, but I believe all of the nations on that list above do allow dual citizenship of some sort. Certainly some of them do, and some of those on that list even currently have some of the easiest citizenship-by-investment programs in the world right now.
Other ones I'll be looking into but aren't on my top priority list until I know more are below. I'll research them more later, but I think all of these except possibly the British Virgin Islands and Haiti do not permit dual citizenship.
Some of these are also not on my priority list because of being dependencies on a 'Western' ZOG nation that I don't trust, even if they are nice places otherwise, but others might be interested:
British Virgin Islands
Cuba
Guadeloupe
Haiti (I think they were listed as allowing dual citizenship)
Martinique
Navassa Island
Netherlands Antilles
Saint Barthelemy
Saint Martin
Trinidad and Tobago (interesting place, but I think no dual citizenship)
Turks and Caicos Islands
Some of these Latin American countries (mostly around the Caribbean Sea) are also interesting, and I think all of the ones on this list except Nicaragua permit dual citizenship:
Belize
Colombia
Costa Rica
Honduras
Nicaragua (no dual)
Panama
Peru
African countries:
At some point I might travel to some African countries too to see what they're like, but I'm concerned about what the ZOGs are doing right now fueling warfare against Russia and imposing dangerous economic sanctions that might be setting the stage for a potential famine that will impact a lot of places in the world, including some countries in Africa.
If we see a period where the world isn't too troubled to travel more widely, I'd be interested in visiting these to see what they were like:
Ghana
Ivory Coast (Côte d'Ivoire)
Kenya
Sao Tome and Principe
The Gambia
Uganda
Not exactly Africa, but an interesting unique island nation east of Madagascar: Mauritius
I need to learn more about these ones below before scheduling any trips, but these might be interesting too:
Angola
Benin
Cape Verde isn't what I'm looking for but might be interesting to others
Madagascar
Rwanda
Tanzania and Zanzibar
Togo
Zambia