This message from Shelby is very interesting. The issue is even more complex than what I believe it was.
The recent versions of the core wallet are only distributing adresses starting with 3. Do anyone know if its possible to generate adresses starting with 1? Most of my stash is on those old "legacy" adresses, but I dont know if any fractions that I move from adresses starting with 3 to these old adresses would be valid (in face of what Shelby explained, assuming its true). Any suggestions?
Through the main Core interface it by default generates an address starting with a 3 but can check a box to generate a bc1 address. I don't see an option anyhere that allows you to generate a legacy format address. I'm not sure if there is a certain command that you can tap into to generate a legacy address, but you can always install a pre Segwit version of core that can be found here;
https://bitcoin.org/bin/Bitcoin Core clients are backwards compatible so you're most likely good to go, the only question is how safe are the older versions today.... If that's not an option then there is Electrum that you can use. They allow you to choose which address format to use.